Method of transforming hfc catv analog fiber transmission to digital fiber tranansmission

ABSTRACT

A method of converting legacy HFC CATV cable systems, which transmit data over the optical fiber portion of the system using the optical counterpart of analog RF waveforms, such as RF QAM waveforms transduced to corresponding optical QAM waveforms, to improved HFC CATV systems that transmit data over the optical fiber using optical fiber optimized protocols, such as Ethernet frames and other optical fiber optimized digital transport protocols. According to the method, most aspects of the legacy HFC CATV system may be retained, however at the CATV head end, the optical fiber transmitter system is replaced by an improved system that extracts the underlying symbols from legacy waveforms, packages these symbols into optical fiber optimized packets, and transmits downstream. The legacy optical fiber nodes are replaced with improved nodes capable of receiving the packets and remodulating the symbols into RF waveforms suitable for injection into the system&#39;s CATV cable.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 13/674,936, “HYBRID ALL DIGITAL FIBER TO CATV CABLE SYSTEM ANDMETHOD”, filed Nov. 12, 2012; this application is also a continuation inpart of of application Ser. No. 13/555,170, “DISTRIBUTED CABLE MODEMTERMINATION SYSTEM WITH SOFTWARE RECONFIGUABLE MAC AND PHY CAPABILITY”,filed Jul. 22, 2012, which in turn claimed the priority benefit of U.S.provisional application 61/511,395, “IMPROVED HYBRID FIBER CABLE SYSTEMAND METHOD”, filed Jul. 25, 2011, and which was also a continuation inpart of application Ser. No. 13/035,993, “METHOD OF CATV CABLESAME-FREQUENCY TIME DIVISION DUPLEX DATA TRANSMISSION”, filed Feb. 27,2011, now U.S. Pat. No. 8,365,237; this application is also acontinuation in part of U.S. patent application Ser. No. 13/478,461,“EFFICIENT BANDWIDTH UTILIZATION METHODS FOR CATV DOCSIS CHANNELS ANDOTHER APPLICATIONS”, filed May 23, 2012, which in turn claimed thepriority benefit of U.S. patent application 61/622,132 entitled“EFFICIENT BANDWIDTH UTILIZATION METHODS FOR CATV DOCSIS CHANNELS ANDOTHER APPLICATIONS”, filed Apr. 10, 2012; this application is also acontinuation in part of U.S. patent application Ser. No. 13/400,415,“METHODS OF ADAPTIVE CANCELLING AND SECONDARY COMMUNICATIONS CHANNELSFOR EXTENDED CAPABILITY HFC CABLE SYSTEMS”, filed Feb. 20, 2012; thisinvention is also a continuation in part of U.S. patent application Ser.No. 13/346,709, “HFC CABLE SYSTEM WITH WIDEBAND COMMUNICATIONS PATHWAYAND COAX DOMAIN NODES”, filed Jan. 9, 2012, which also claimed thepriority benefit of U.S. provisional patent application 61/385,125 filedSep. 21, 2010, and which was also a continuation in part of applicationSer. No. 12/692,528, “DISTRIBUTED CABLE MODEM TERMINATION SYSTEM” filedJan. 22, 2010, now U.S. Pat. No. 8,311,412; all have the inventor ShlomoSelim Rakib; the contents of all of these applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Cable television (CATV), originally introduced in the late 1940's as away to transmit television signals by coaxial cables to houses in areasof poor reception, has over the years been modified and extended toenable the cable medium to transport a growing number of different typesof digital data, including both digital television and broadbandInternet data.

Over the years, this 1940's and 1950's era system has been extended toprovide more and more functionality. In recent years, the CATV systemhas been extended by the use of optical fibers to handle much of theload of transmitting data from the many different CATV cables handlinglocal neighborhoods, and the cable head or operator of the system. Herethe data will often be transmitted for long distances using opticalfiber, and the optical (usually infrared light) signals then transformedto the radiofrequency (RF) signals used to communicate over CATV cable(usually in the 5 MHz to 1-GHz frequencies) by many local optical fibernodes. Such systems are often referred to as hybrid fiber cable systems,or HFC systems. The complex electronics that are used by the cableoperator to inject signals (e.g. data) into the system, as well asextract signals (e.g. data) from the system are often referred to asCable Modem Termination Systems or CMTS systems.

A more detailed discussion of prior art in this field can be found inU.S. Pat. No. 8,311,412, the contents of which are incorporated hereinby reference.

Prior art work with various types of CMTS systems and fiber nodesincludes Liva et. al., U.S. Pat. No. 7,149,223; Sucharczuk et. al. USpatent application 2007/0189770; Sawyer et. al., US patent application2003/0066087; and Amit, U.S. Pat. No. 7,197,045.

BRIEF SUMMARY OF THE INVENTION

As user demand for ever increasing amounts of downstream and upstreambandwidth increases, further improvement and advances in HFC technologyare needed.

The invention is based, in part, upon the realization that in order tomake further advances in HFC technology, deviations from both the priorart schemes to allocate upstream and downstream data on the CATV portionof the HFC network, and deviations from the prior art schemes toallocate upstream and downstream data on the fiber portion of the HFCsystem, would be useful.

The optical waveforms presently used on the fiber portion of opticalfiber wavelengths of present HFC systems are often just frequencyshifted versions of the same waveforms used to transmit RF signals onthe CATV cable. Although these direct RF to optical and back to RFwaveform reproduction methods have the advantage of simplicity, due tovarious optical fiber signal propagation effects, such as Ramanscattering, such RF to optical shifted CATV waveforms make inefficientuse of available optical fiber spectrum. This is because due to thesevarious optical fiber effects, the various waveforms become smeared ordistorted, resulting in crosstalk between neighboring optical fiberwavelengths, and the optical versions of the basic RF CATV waveforms arenot at all optimized to cope with these effects.

The invention is based, in part, on the insight that by shifting toalternative types of waveforms, such as the waveforms used to transmitGigabyte Ethernet (GigE) signals (which often use more distortionresistant waveforms such as binary phase shift keyed (BPSK) orquadraphase-shift keying (QPSK) modulation), a much higher amount ofdata may be sent over the optical fiber. The rate of data transmissionper wavelength can be much higher, and different wavelengths may bespaced much closer together. Other benefits, such as lower noise level,and less power utilization, may also be realized.

The burdens of shifting from legacy HFC systems, which operate byessentially sending the optical counterparts of standard CATV RFwaveforms, such as optical versions of QAM waveforms, over opticalfiber, to a more advanced system that operates with alternative types ofwaveforms, should be appreciated. Over the years, there has been anexpenditure of tens of billions of dollars or more in legacy HFC systeminfrastructure, along with a huge investment in various software systemsto manage this legacy infrastructure. It is simply not practical toscrap this massive investment overnight.

The invention is also based, in part, on the insight that to minimizethe cost of transitioning to a next-generation digital optical fiberbased HFC system, those solutions that at least initially preserve largeportions of legacy HFC systems, while also providing the benefits ofdigital optical fiber transmission, will often be preferable. Inparticular, “plug-in” head-end solutions, which enable legacy HFC headend systems to continue to operate by generating various RF waveforms atthe head end, but which then efficiently demodulate or digitize these RFwaveforms for optical fiber transmission have benefits in this regard.These “plug-in” head end solutions will work in conjunction with“plug-in” optical fiber node solutions that can then also efficientlyremodulate, or digital to analog convert, the digital optical fiber databack into various RF waveforms suitable for injection into neighborhoodCATV cable. Such “plug-in” solutions can, for example, minimize theburden of writing new management software because the process ofdemodulating or digitizing RF waveforms, although of course requiringsome hardware for this purpose, is from a software perspectiverelatively simple. Even the process of compressing and decompressingthis data before and after digital optical fiber transmission is alsorelatively simple. Similarly the process of taking the opticallytransmitted demodulated data or digitized data and in turn using it tomodulate various CATV RF transmitters (or digital to analog converters)at the optical fiber node, although again requiring some new opticalfiber node hardware, is also not complex from the software perspective.To the operator of the HFC system, the transition to digital opticalfiber transmission can be, at least at first, almost totallytransparent. The operator can continue to operate the head end usinglegacy software and systems, yet reap the benefits of digital opticalfiber data transmission.

An additional advantage is that once suitable next generation digitalfiber optic nodes (DOFN) are in place, the HFC system operator thengains the freedom to make additional head end improvements. Inparticular, legacy equipment that generates head end RF waveforms cangradually be phased out, and the head end equipment eventually bereplaced with equipment that simply transmits digital data to thevarious CATV digital optical fiber nodes, according to a schedule thatmakes sense to the HFC system operator. The invention thus provides agentle path that allows a legacy HFC system to be upgraded to a moreefficient and more flexible all-digital (at least prior to the actualneighborhood CATV cable, which may still rely on RF waveforms asdesired) system as a gradual series of steps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overall view of the various frequencies and datachannels that are presently allocated for a typical CATV cable carryinglegacy analog television FDM channels, QAM digital television channels,and various types of DOCSIS data.

FIG. 2 shows an overall view of the various wavelengths allocated forprior art optical fiber wavelength division multiplexing schemes (150)and dense wavelength division multiplexing (DWDM) schemes (160).Although the present invention may use DWDM methods, it does not requirethem, and to some extent reduces the need for DWDM methods because itcan fit more types of digital data onto a single wavelength using, forexample, GigE optical data packets (170).

FIG. 3 shows a simplified version of how prior art HFC systems transmitdata from the cable head to different optical fiber nodes servingdifferent neighborhoods.

FIG. 4A shows an overview of how the invention may be used to upgrade alegacy analog optical fiber based HFC CATV cable system by replacing theanalog modulators and demodulators on either end of the system withdigital demodulators and remodulators.

FIG. 4B shows a more detailed overview of how the invention may be usedto upgrade a legacy analog optical fiber based HFC CATV cable systemthat is was transmitting a mixture of consisting of a plurality of videoQAM channels and IP data, such as DOCSIS IP data. Here the legacy QAMchannels may be demodulated into their underlying QAM constellationsymbols. This QAM symbol data, along with the legacy IP data, can beencapsulated into various digital optical data packets, and transmittedover the optical fiber in this more efficient form. At the optical fibernode, the data packets can be parsed, and the QAM channels regeneratedby remodulated by using the QAM constellation symbols to drive variousoptical fiber node QAM RF transmitters. The data may also be suitablycompressed and decompressed, as desired, to further improve theefficiency and speed of data transmission. The IP data can also beextracted from the optical data packets, and used to feed an opticalfiber node based CMTS system.

FIG. 4C shows still more detailed of how the invention may be used toupgrade a legacy analog optical fiber based HFC CATV cable system thatis was transmitting a mixture of consisting of a plurality of legacyvideo QAM channels, other analog RF channels such legacy NTSC videochannels, and legacy IP data, such as DOCSIS IP data. Here the legacyQAM channels may be demodulated into their underlying QAM constellationsymbols. The other RF video channels may be handled by digitization andoptional compression, as desired. This QAM symbol data, digitized RFchannel data and the legacy IP data, can be encapsulated into variousdigital optical data packets, and transmitted over the optical fiber. Atthe DOFN optical fiber node, the data packets can be parsed, and the QAMchannels regenerated or remodulated by using the QAM constellationsymbols to drive various optical fiber node QAM RF transmitters, and thedigized analog RF channels optionally decompressed and fed into anelectrical system comprising a digital to analog converter to regeneratethe analog RF channels. The three types of RF waveforms can then becombined and injected into the neighborhood CATV cable system as before.

FIG. 4D contrasts the difference in downstream data transmission betweena prior art HFC system that operates using a 1310 nm optical fiberinfrared signal analog according to typical CATV waveforms (e.g. manyQAM waveforms), and the invention's improved digital transmissionmethods. In contrast to prior art, because the invention can transmitall CATV data in digital form using various data packets, the highereffective data rate and superior addressing capability of IP datapackets allows more different types of data to be sent on the samewavelength. The invention preserves backward compatibility by providingvarious converters to convert back and forth between legacy waveformsand IP data packets.

FIG. 5 shows an overview of the invention in operation in downstreammode, showing how the improved “smart” D-CMRTS fiber nodes can transporta higher effective amount of customized data downstream for users.

FIG. 6 shows how the invention may also reparation the CATVupstream/downstream frequency split from the standard (US) 5-42 MHzupstream frequency range, into an alternate and often broader upstreamfrequency range. This helps the system transmit a far greater amount ofupstream data from local neighborhoods to the cable head.

FIG. 7 shows a more detailed view showing one embodiment of how theD-CMRTS fiber nodes may operate.

FIG. 8 shows additional details of how the CMRTS portion of the D-CMRTSfiber node may operate. The CMRTS portion provides much of the higherfunctionality of the system.

FIG. 9 shows more details of how the virtual shelf manager and theconfiguration database may control the functionality of most or all ofthe various D-CMRTS fiber nodes, and optionally other active nodes andswitches in the HFC network system.

FIG. 10 shows a residential gateway (1100) that can also convert betweena CATV cable system with an extended frequency allocated for upstreamdata (e.g. 5-547 MHz or alternative upstream range of frequencies), andresidential equipment designed for the standard 5-42 MHz range ofupstream frequencies.

DETAILED DESCRIPTION OF THE INVENTION

Nomenclature: In this specification, the term “legacy signals” whenpertaining to RF waveforms, will often be used to describe various olderstandard CATV RF signals such as NTSC (television) signals, FM radiosignals, set top box signals and the like. It should be understood,however, that the invention's methods will in fact operate with any typeof RF signal. Thus the term legacy signals, although intended to improvereadability by reminding the reader that the invention's methods areparticularly useful for coping with various CATV legacy RF waveforms, isnot otherwise intended to be limiting.

Legacy signals, when pertaining to optical fiber transmission methods,will generally refer to prior art methods which simply transformed theRF waveforms, such as QAM RF waveforms, into optical waveforms whileretaining the essential characteristics (e.g. shape) of the RFwaveforms.

Continued discussion:

Although this particular specification is more focused on the opticalfiber portion of the HFC system, it should be noted that as the opticalfiber portion of the system is upgraded, so to further upgrades in theCATV cable portion of the CATV system are also possible. For the sake ofcompleteness, and to provide an overall picture of how many of theseimprovements can be combined to incrementally produce a very advancedHFC system, these various CATV cable system upgrades will also bedescribed.

As discussed in previous specification in this series of patentapplications, the radio-frequency (RF) side of the HFC network, the CATVspectrum is also used inefficiently. Much of the available 5 MHz toapproximately 1 GHz CATV frequency is presently filled up with QAMchannels that, most of the time, are carrying downstream data that isnot actually being used (at that time) by the various households thatare connected to the cable. Another problem is that only a tiny regionof CATV spectrum (usually 5-42 MHz), is allocated for upstream data.This relatively narrow region of frequencies must carry the upstreamdata for the entire CATV neighborhood. This results in great limitationson the bandwidth or amount of data that can be uploaded from the varioushouseholds. Thus typical CATV systems are asymmetric, with thedownstream data rates being much higher than the upstream data rates.

Thus this invention, or series of inventions, teaches new HFC systemsand methods to carry much higher amounts of upstream and downstreamdata. On the fiber portion of the HFC system, the invention teaches useof non-CATV compatible waveforms (e.g. GigE rather than QAM waveforms)which can carry much higher amounts of data over long distances. On thecable portion of the HFC system, other inventions in this series teachimproved systems and methods that utilize the limited 5 MHz to 1-GHzbandwidth of CATV cable more efficiently.

The invention operates, in part, by use of intelligent optical fibernodes, and is in part a further extension of the CMRTS optical fibernodes previously discussed by the previously discussed copending USpatent applications.

In some embodiments, the invention may be a system or a method based ondigital optical fiber nodes operating in a Hybrid-Fiber CATV-Cable (HFC)network. Such systems generally comprise a cable head end, which isoften in IP communication with an IP backbone such as the Internet orother high speed digital network. These HFC networks also generally alsocomprise one or more optical fibers in communication with the head end,as well as at least one and often many digital optical fiber nodes(DOFN).

These digital optical fiber nodes have some elements in common with theCable Modem Remote Termination Systems (CMRTS) and Digital Cable ModemRemote Termination systems (D-CMRTS) previously described in variouscopending applications such as parent U.S. applications Ser. No.12/692,582, 61/385,125, Ser. No. 12/907,970, Ser. No. 13/346,709, Ser.No. 13/478,461, and Ser. No. 13/555,170, and Ser. No. 13/674,936 thecontents of which are incorporated herein by reference. As a result,these digital optical fiber nodes (DOFN) will frequently be discussed inthe alternative in this disclosure as D-CMRTS units.

To form an HFC system, these various DOFN or D-CMRTS units will beconnected to (i.e. in RF communication with) various CATV cables (e.g.coax cable, capable of RF transmissions), and at least one CATV cabledevice which will be various cable modems, set top boxes, digitaltelevisions, computers, and the like.

Although, as discussed in the earlier disclosures, the inventor'searlier D-CMRTS units were designed from the beginning with a highcapability to provide additional data handing capability to CATV systems(e.g. above and beyond the present DOCSIS 3.0 standard), one challengingproblem is how to provide even more functionality while still providingthe ability to gracefully operate in an environment with large amountsof legacy equipment.

A unique aspect of the present disclosure is that the improved DOFN orD-CMRTS units disclosed herein, while providing advanced functionality,and often totally abandoning use of optical versions of the standardQAM, NTSC, FM waveforms on optical fiber, are still highly capable ofoperating with legacy equipment.

Here, systems are disclosed that are designed with a high capability tooperate in the digital optical fiber domain (e.g. using optical fiberdigital transport protocols such as GigE) while still providing CATV RFsignals carrying various types of legacy analog CATV RF waveforms, suchas analog NTSC television channels, FM audio channels, QPSK channels,QAM channels and the like. The present methods have the additionaladvantage that because digital data transport protocols can easily carrydata packets to and from many alternative addresses, the invention'smethods can operate without requiring the use of, for example, largenumbers of alternative optical fiber wavelengths. By contrast, underprior art methods, use of large numbers of alternative optical fiberwavelengths was required in order to accommodate the many differenttypes of analog legacy CATV waveforms that can originate from manydifferent types of legacy optical fiber nodes.

According to the invention, such improvements can be made by, forexample, converting legacy CATV analog waveforms to a digital form byhigh speed analog to digital converters and or QAM waveform demodulationinto the underlying QAM symbols. This approach has the advantage thatthese waveforms can then be transformed to digital data packets (IP datapackets) without the system otherwise needing to understand what theunderlying data content of the waveforms is.

(For further discussion on QAM symbol methods, please see copendingapplication Ser. No. 13/478,461 “EFFICIENT BANDWIDTH UTILIZATION METHODSFOR CATV DOCSIS CHANNELS AND OTHER APPLICATIONS”, the contents of whichare incorporated herein by reference.)

The digitized waveform data can then be transported as IP packets overthe HFC optical fibers using digital optical fiber data transmissionformat such as GigE.

More specifically, CATV legacy downstream RF waveforms of any type (e.g.NTSC, FM, QPSK) and/or more standard CATV downstream RF waveforms suchas various QAM waveforms can be digitized by using a high speed analogto digital converter or other method to sample and digitize these legacydownstream RF waveforms, thus producing digital samples of the legacydownstream RF waveforms. This digital data which can then be convertedto IP packets and sent over the optical fiber. Alternatively, and moreefficiently in the case where more standard RF QAM waveforms are beingtransmitted downstream, these RF QAM waveforms, which are complexwaveforms constructed using various underlying QAM symbols, may bedemodulated and the underlying QAM symbols determined. These demodulatedQAM symbols can then also be converted to various data packets andoptically transmitted downstream over the HFC optical fiber or fibers.

Once in the form of IP data packets, low cost equipment such asinexpensive switches can then be used to easily sort and transport theseIP data packets to and from various devices.

To reconstruct these various legacy CATV RF waveforms, at the digitaloptical fiber node(s) or D-CMRTS unit(s), various RF digitalreconstitution devices may be configured to accept the digital samplesof downstream RF waveforms (which were digitally transmitted downstreamover the optical fiber), and reconstitute these digital waveform samplesinto one or more downstream digitally reconstituted RF waveformschannels that essentially reproduce the original RF waveforms.

Alternatively or additionally, at the digital optical fiber node(s) orD-CMRTS unit(s) there can also be one or more remodulator devicesconfigured to accept the downstream digital QAM symbols that weretransmitted over the optical fiber, and remodulate these QAM symbolsinto one or more downstream QAM symbol, again producing remodulated RFQAM waveforms and channels that essentially reproduce the original RFQAM channels.

To provide still higher levels of service (e.g. to provide higher CATVdata carrying capability, and provide functionality beyond the presentDOCSIS 3.0 standard), the digital optical fiber nodes or D-CMRTS unitswill often also contain one or more IP to QAM conversion devices such asQAM modulators. These QAM modulators may be configured to acceptdownstream digital IP data packets transmitted over the optical fiber,and to modulate these digital IP data packets into one or moredownstream IP based RF QAM channels. These can be broadcast QAMchannels, narrowcast QAM channels, on-demand QAM channels, and so on.

Often, according to the invention, the digital optical fiber nodes orD-CMRTS units will employ two or more of the above options, and willthus use a RF combiner device configured to combine any of thesedigitally reconstituted RF channels, QAM symbol remodulated RF QAMchannels and these IP based RF QAM channels, and then transmit thesevarious RF channels downstream over the CATV cable to the various CATVcable devices.

In one embodiment, the invention may further be a method of convertinglegacy HFC CATV cable systems, which transmit data over the opticalfiber portion of the system using the optical counterpart of analog RFwaveforms, such as RF QAM waveforms transduced to corresponding opticalQAM waveforms, to improved HFC CATV systems that transmit data over theoptical fiber using optical fiber optimized protocols, such as Ethernetframes and other optical fiber optimized digital transport protocols.According to the method, most aspects of the legacy HFC CATV system maybe retained, however at the CATV head end, the optical fiber transmittersystem is replaced by an improved system that extracts the underlyingsymbols from legacy waveforms, packages these symbols into optical fiberoptimized packets, and transmits downstream. The legacy optical fibernodes are replaced with improved optical fiber nodes capable ofreceiving the packets and remodulating the symbols into RF waveformssuitable for injection into the system's CATV cable.

Optical fiber data transmission methods:

As previously discussed, prior art schemes of transmitting HFC data inthe form of one or more CATV analog modulated wavelengths of light,along optical fiber, tended to be inefficient. That is, the prior artmethods limited the amount of data that could be sent. This is becausethe analog waveforms used to transmit RF signals on CATV cable workinefficiently when transposed to optical wavelengths. Due to variouseffects including Raman scattering, and other nonlinear optical fibereffects, when too many analog modulated light wavelengths are placedonto an optical fiber too close together (in terms of wavelengthdifferences), cross-talk between the different wavelengths tends todegrade the complex CATV RF analog signals (usually composed of many QAMmodulated waveforms) to the point where crosstalk may render the signalsuseless.

As a result, to prevent the CATV modulated analog signal fromdegradation when carried over optical fiber, the wavelengths must berather widely spread out. Thus due to cross talk effects, an opticalfiber may only be capable of transmitting a few (e.g. 8) inefficientlymodulated CATV signals, each transmitting about 6 Gigabits of data persecond.

By contrast, if more efficiently digitally modulated signals (e.g. GigEdata formats) were used, the same stretch of optical fiber might becapable of transmitting many more wavelengths (e.g. 80) of signals, andeach wavelength in turn may transmit far more data, such as between10-100 Gigabits of data per second.

Application Ser. No. 12/692,582, now (U.S. Pat. No. 8,311,412) taughtthe advantages of producing a new type of optical fiber node, therecalled a Cable Modem Remote Termination System (CMRTS) device, whichessentially pushed much of the functionality (such as generating QAMsignals) of the prior art Cable Modem Termination Systems (CMTS) fromthe central cable head down to many distributed optical fiber nodesservicing neighborhood CATV cables. Thus according to application Ser.No. 12/692,582, non-CATV compliant signals may be sent to and from thecentral cable head to various remote CMRTS optical fiber nodes byoptical fibers carrying light modulated by more efficient digitalEthernet protocols (e.g. GigE signals). The CMRTS optical fiber nodesthen converts these non-CATV compliant signals into CATV compliant RFsignals, such as a plurality of different RF QAM modulated signals,and/or other types of signals.

Parent and copending application Ser. No. 13/674,936, which was a CIP ofSer. No. 12/692,582, further built upon this concept, and further taughtthe advantages that can be obtained by reducing or dropping additionalbackward compatibility requirements, such as the requirement that legacyRF waveforms (e.g. QAM waveforms) be transmitted along the HFC opticalfiber(s) while preserving the essential waveform characteristics (e.g.requiring that the optical QAM waveforms be the same as the RF QAMwaveforms).

Other departures from pure backward compatibility may also be reduced.For example, according to the invention, the prior art CATV upstreamrequirements that upstream data must be carried as a number of 2 MHzwide QAM channels in the 5-42 MHz region, may be dropped in favor ofalternate upstream schemes that provide for greater amounts of upstreamdata to be transmitted. That is the 5-42 MHz region may be extended intothe higher frequency ranges—for example extended to the 5-547 MHzregion, which will allow for a higher rate of upstream data to betransmitted, but of course will cut into the rate of transmission ofdownstream data.

However even if the upstream bandwidth problem is solved at the CATVcable side of the HFC system, the optical fiber itself, if usedaccording to prior art schemes (e.g. shove the analog signal over theoptical fiber in an essentially unchanged form) will now be ratelimiting. That is, if a large number of different neighborhoods, eachwith their own stretch of CATV cable, are now enabled to starttransmitting much more upstream data, unless the method of sending dataover the fiber portion of the HFC network is changed, there will soon bea bottleneck at the fiber stage. This is because the prior art HFCmethods of handing upstream data would, in general, simply convert theanalog RF modulated CATV upstream waveforms into equivalently modulatedoptical fiber infrared light waveforms, and then transmit this data backover the optical fiber. Although such conversion processes can be easilydone with inexpensive converters, this scheme has the drawback, aspreviously discussed, that they are not optimized for optical fiber.Consider the problem of pooling upstream data from multipleneighborhoods. Although the data CATV RF data from each neighborhoodmight be converted to a slightly different infrared frequency, put onoptical fibers, the fibers combined and a composite multiple wavelengthsignals sent upstream, the inefficient CATV RF modulation schemes meanthat each wavelength will carry only a relatively small amount of data.Further, due to crosstalk effects, the number of different neighborhoodsworth of data that can be pooled is also limited. So due to prior-artinefficiencies, the potentially very large ability of the optical fiberto carry upstream data rapidly becomes limiting.

However, again by reducing the requirements that the HFC system be fullybackward compatible in terms of inefficiently carrying legacy analog RFwaveforms over optical fiber; the much higher amount of upstreambandwidth that would be generated under the invention can now be handledby repackaging the upstream data into more efficient modulation formats,such as the digital (GigE) modulation format, before transmitting thedata on the optical fiber. Thus, according to the present invention, asmaller number of higher data density and more efficiently modulatedoptical fiber optimized signals, such as GigE data packets may now sent.This overcomes the inefficiencies of prior-art optical fiber modulationschemes, and helps remove the optical fiber upstream transmissionbottleneck.

As per parent applications Ser. No. 12/692,582 and Ser. No. 13/674,936,the present disclosure relies, in part, upon a radically different CMTSdesign in which the QAM modulators in the CMTS PHY section (used toultimately provide the waveforms used to send RF data signals to a givenindividual cable) are often not located at the central cable head, butrather are divided and pushed out to the distant optical fiber nodes ofthe HFC network. That is, in contrast to prior art designs, were the QAMmodulators were are located in the PHY units of main (centralized,e.g.—cable head) CMTS line cards on the central CMTS units; in thepresent invention, some or all of the QAM modulators are located in thePHY sections of remote or distributed CMRTS optical fiber nodes.

Parent application Ser. No. 13/674,936 taught that, as a less favoredembodiment, and when greater compatibility with legacy equipment isdesired, at least some of the QAM modulators, or other RF signalgenerators such as NTSC television, FM radio, set top box QPSK signalsand the like can still remain at the head end.

Here, in the present specification, in the preferred embodiment, alllegacy RF waveforms output by the legacy head end equipment will usuallybe digitized before optical transmission. This digitization can be doneby various means, including high frequency analog to digital sampling,or by for example demodulating various QAM or OFDM waveforms,determining the underlying QAM or OFDM symbols used to generate the QAMor OFDM waveforms, and digitally sending the results. At the opticalfiber node, these RF waveforms can then be regenerated, for example bydigital to analog conversion and RF modulation, or using the digitallysent QAM or OFDM symbols to control one or more RF QAM or OFDMmodulators.

Thus often it will be useful to transmit the data downstream to thevarious optical fiber nodes in the form of standard IP packet typedigital data, as well as receive upstream data in digital form as well.The optical fiber nodes can examine the data packets, determine whichpackets correspond to what signals, and for example then use theappropriate data packets to drive various optical fiber located RF QAMmodulators (e.g. for broadcast QAM signals, narrowcast QAM signals,DOCSIS QAM signals, etc.) as desired.

In the prior Ser. No. 12/692,582 application, these advanced opticalfiber nodes with local QAM modulators were called Cable Modem RemoteTermination System (CMRTS) units. In other applications in this series,to better emphasize that some embodiments of these units could functionusing Digital Wavelength Division Multiplexing (e.g. use of alternatedata transmission formats such as 1GigE, 10GigE, EPON, BPON, GPON,10GPON, SONET, Fiber Channel, FSAN, and the like) alternativeembodiments of the CMRTS units of the present invention were termedD-CMRTS units, where the D may be used to symbolize the Digitalencoding/decoding methods of the D-CMRTS units with respect to legacysignals. In the present application, because here as well, alternativedigital optical fiber data transmission methods are also taught, to someextent this earlier D-CMRTS nomenclature, as an alternative to theDigital Optical Fiber Node or (DOFN) nomenclature, will be retained.Note however that the particular DOFN nodes taught in this specificationare properly defined in the claims, and the earlier D-CMRTS teachingreiterated in this specification, although useful for helping to definevarious useful alternative DOFN embodiments, is not intended to belimiting.

To better emphasize the changes in functionality at the head end of theHFC system, the higher capacity cable modem termination system (CMTS) atthe head end will often be referred to as D-CMTS units, where the Dagain is used to symbolize the digital encoding capability of the D-CMTSunits. The output from these units are generally used to drive one ormore head-end optical fiber lasers (e.g. optical transmitters). Theseoptical fiber laser transmitters, and their associated electronicequipment, are often referred to as legacy optical fiber transmittersystems.

As per the CMRTS units that were previously disclosed in Ser. No.12/692,582, the D-CMRTS/DOFN units disclosed herein will often also belocated at the final network fiber nodes (FN) between the fiber portionsof the HFC system, and the cable portions of the HFC system.

In the CMTS systems discussed in Ser. No. 12/692,582, some QAMmodulators were located in the centralized CMTS PHY sections at thecable head, while some QAM modulators were located at the remote CMRTSunits. The CMTS QAM modulators were used for sending data, such as astandardized package of cable TV channels and perhaps a basic level ofDOCSIS service, which might be generally requested by manyneighborhoods; over optical fiber using RF CATV (e.g. QAM) modulatedinfrared light signals. This helped maintain backward compatibility withprior art HFC systems.

In this present disclosure, in order to focus on aspects of theinvention that can provide higher amounts of upstream and downstreamdata to subscribers, this type of backward compatibility is lesspreferred. In preferred embodiments, all data traveling over the opticalfiber will be digitally encoded according to optical fiber optimizedformats, rather than simply optical versions of legacy RF waveforms.

Here, as needed to maintain backward compatibility, the various legacyhead end waveforms, such as QAM waveforms, NTSC television waveforms,QPSK waveforms and the like (during transmission over optical fiber bothdownstream from the head end to the optical fiber nodes, and upstreamfrom the optical fiber nodes to the head end) can be digitized fortransmission by various methods, and then reconstituted after opticalfiber transmission. As previously discussed, these digitization methodscan range from brute force (i.e. simple high speed analog to digitalsampling at around the Nyquist frequency (e.g. 2× the highest frequencyof the underlying waveform), as well as more sophisticated methods suchas demodulating the various QAM or OFDM waveforms to extract theunderlying QAM or OFDM symbols used to produce the RF waveforms in thefirst place.

Often the brute force, high frequency analog to digital sampling methodsmay be more suitable for legacy NTSC, FM, or QPSK waveforms (channels).By contrast, QAM or OFDM demodulation methods may be more suitable forQAM channels transmitting various SD or HD digital television, DOCSISQAM or OFDM channels, and the like.

Thus some embodiments of the present invention may elect to have no QAMmodulators at the cable head whatsoever, and send pure non-CATVcompatible waveforms (e.g. digital IP data packets) through the opticalfibers. These systems may rely on the remote D-CMRTS/DOFN units togenerate all of the downstream QAM signals in the system.

Thus in one embodiment, the invention may be a method for enhancing thedata carrying capacity of a hybrid fiber cable (HFC) network with acable head, an optical fiber network, a plurality of optical fibernodes, a plurality of individual CATV cables connected to the pluralityof optical fiber nodes (D-CMRTS units), and a plurality of individualcable modems, each with differing data requirements, connected to eachof the individual CATV cables.

This method may work by using at least one optical fiber, operating atone or more wavelengths, to transport a first set of downstream datafrom the cable head to the optical fiber nodes. This first set ofdownstream data may be transmitted in a digital format that is notcapable of being directly injected into individual CATV cables by simpleoptical to RF converters.

Here, generally so much data may be transmitted that if all of the firstset of downstream data was converted into RF QAM waveforms, thebandwidth of this data would exceed the available bandwidth of any ofthe individual CATV cables in the system. To avoid this problem,generally only a selected portion of this first set of downstream datawill be converted into downstream RF QAM waveforms at these opticalfiber nodes.

What portions of the optical fiber downstream data are selected for anygiven CATV cable neighborhood (with its own optical fiber node and CATVcable) may differ. At the optical fiber nodes, data packets will beselected, and these selected data packets will be converted intodownstream RF QAM waveforms that in turn will be injected into theindividual CATV cables.

Here, the main constraint is that for each individual CATV cable thedownstream RF QAM waveforms should be selected so that the sum total ofthe selected downstream RF QAM waveforms do not exceed the availablebandwidth of the individual CATV cables.

In a preferred embodiment, the invention's D-CMRTS/DOFN units will oftenbe designed to be highly software configurable, so that the ability ofthe D-CMRTS/DOFN units to operate their remote or distributed QAMmodulators to send downstream data, as well as the ability of theD-CMRTS/DOFN units to operate various RF packet processors that receivemultiple RF bursts of modulated upstream data from various cable modems,demodulate the bursts, digitize and reassemble this upstream data intopackets, and retransmit this data back upstream, can be reconfigured byremote software. Such methods can greatly simplify the management andconfiguration of the distributed D-CMRTS/DOFN network.

As one simplified example, in order to supply a standardized set of TVchannels and other services to three cables in three neighborhoods, thelegacy head end equipment may have QAM modulators in their PHY units(See FIG. 7, 614) set to drive an optical fiber with multiple QAMsignals at optical wavelengths.

To convert to all digital optical fiber transmission, while maintaininghigh levels of backward compatibility, the head end may have digitalconverter units (399), occasionally referred to in the alternative as adigital optical fiber transmitter system, that can intercept output fromthe legacy head end QAM, FM, QPSK modulators and other RF modulators(614), and digitize this output by relatively unintelligent methods(high speed analog to digital converters, QAM or OFDM waveformdemodulation into QAM or OFDM symbols). The digital output from theseconverters can then be packaged into appropriate digital data packets,such as GigE data packets, and transmitted along optical fiber (218)along with other digital traffic (e.g. from GigE PHY modulators 620) tothe optical fiber nodes.

In some neighborhoods, simple “dumb” converters and “dumb” optical fibernodes can take this digital data from the legacy head end equipment(614), and convert it back to legacy QAM, FM and QPSK signals by varioussimple methods such as digital to analog conversion (600), QAMremodulation using the QAM symbols (603), and the like. These “dumb”converters and optical fiber nodes can then inject these reconstitutedRF signals into those neighborhood CATV cables (226) that are equippedwith “dumb” converters and optical fiber nodes.

In some embodiments, the cable head end may have no QAM modulators (orother modulators such as FM and QPSK modulators in their CATV PHY units614), and all signals going out to the various D-CMTRS/DOFN opticalfiber nodes along the fiber portion of the network (218) may bedigitally modulated in GigE or other format.

Some of the examples in this specification, such as FIG. 7, show a mixedmode of operation, where some legacy “dumb” converters and optical fibernodes in some neighborhoods work in conjunction with more advancedD-CMRTS optical fiber nodes in other neighborhoods. Other examples showa pure GigE mode where backward compatibility with dumb optical fibernodes is no longer required. One advantage of the invention is that

Since the D-CMRTS units will often use optical fibers and variousDigital Ethernet (GigE) protocols as their primary means ofcommunication, this GigE fiber data will require conversion,reformatting, and QAM modulation by the components (e.g. 600, 603) inthe remote D-CMRTS units (304). The QAM modulators in the D-CMRTS unitswill then provide a radiofrequency (RF) QAM signal that can be injectedinto the cable, and recognized by cable modems attached to the variouscables.

As previously discussed, one of the biggest advantages of generatingsome or all of the CATV RF data at the local D-CMRTS optical fiber nodeis that vast amounts of data can be carried by the optical fiber usingmodulation schemes, such as the various digital GigE data transmissionschemes, that may be optimized for the signal transmissioncharacteristics of the optical fiber media. That is, by eliminating theneed for direct and simple conversion to and from the signal waveforms(often QAM waveforms) used to send RF data on CATV cables, the opticalfiber signals can both carry more data per wavelength, and also allowfor a greater number of signals at nearby optical fiber wavelengths tobe sent with minimal interference.

As per the prior Ser. No. 12/692,582 disclosure, the present disclosurealso relies, in part, upon the observation that at the present level ofrather coarse granularity (where multiple neighborhoods are served bythe same CATV QAM signals) the aggregate demands for IP-on demand datafrom multiple cables serving multiple neighborhoods may easily saturatethe limited CATV bandwidth. That is, absent some sort of customization,it is not possible to send all data to everybody because it won't fit onthe CATV cable. However at a finer level of granularity (where eachneighborhood might get its own customized CATV signal), the IP-on demanddata for an individual neighborhood is more likely to fit within thelimited bandwidth of each neighborhood's CATV cable.

The trick is thus to avoid overloading each neighborhood's particularCATV cable bandwidth by picking and choosing the mix of standard QAM andQAM IP/on-demand signals are delivered to each neighborhood.

Software control methods:

As previously discussed, one large advantage of the present inventionsystems and methods is that they allow the cable operator to largelypreserve use of legacy HFC control software, to the point where at leastinitially, an upgrade to an all digital optical fiber data transmissionscheme can be largely software transparent to both the cable operator aswell as the various CATV user households as well.

However because the invention also allows, at least after the initialconversion to all digital optical fiber data transmission schemes, forstill more advanced functionality to be implemented as desired, thesemore advanced (non-transparent) software control methods will also bedescribed.

For more advanced functionality, it may be useful to adopt some of thecomputer control systems previously discussed for Ser. No. 12/692,582,incorporated herein by reference.

A more advanced (i.e. non-legacy) computer control system may, forexample, manage the available bandwidth on the various cables that servethe various neighborhoods. When used in a less backward compatible,higher performance mode, such as a phase 3 upgrade step to be discussedlater on in this specification, the computerized system may vary boththe “standard” QAM channels (if any) being transmitted by any givencentral D-CMRT line card, as well as the user-customized or “premium”IP/on-demand QAM or edge QAM channels being transmitted by the remoteD-CMRTS/DOFN units.

In CATV jargon, the various CMTS systems at the cable head are oftenreferred to as a “shelf” or “CMTS shelf” (500). In some embodiments, theinvention may further distribute the functionality of the CMTS unit fromthe cable head to D-CMRTS/DOFN units that may be distributed to thefar-flung optical fiber nodes throughout the entire network.

In both situations where use of legacy control software is desired, aswell as in situations where more advanced control software is desired,from a network management perspective, it is often simpler for the othernetwork equipment and software to continue to communicate with thisnetwork distributed D-CMRTS/DOFN units as if it was still a single cablehead CMTS (500). Thus, in one embodiment, this computer control systemand software that manages the network distributed CMTS will also becalled “virtual shelf” hardware and software, because the computercontrol system may both manage the complex configuration issues involvedin running a distributed CMTS system, and then shield this complexityfrom the rest of the system when needed. Thus the remainder of the cablehead system need not be redesigned to handle the distributed CMTSfunctionality, but may continue to address the invention's distributedCMTS as if it was a prior art non-distributed CMTS.

Thus, in some embodiments, the virtual shelf hardware/software systemmay, for example, take as inputs, user demand over multipleneighborhoods for basic TV channels and basic DOCSIS services, userdemand in individual neighborhoods for advanced or premium on-demand TVor premium DOCSIS IP service (IP-on demand), and the limited number oftotal QAM channels that can be carried over cable.

In the first option, the virtual shelf system will simply work usingwhatever empty QAM channels are made available by the cable operator,and will work to optimize data to users within this overall constraint.

In the second option, in order to send still more data, the virtualshelf system may be much more active. It may, for example, elect todirect the QAM modulators in the PHY unit of a head end line card (614)to stop sending signals on one QAM channel (frequency), in order to freeup this QAM channel (frequency) for a neighborhood specific QAM channel(frequency). For this invention, often this process may be taken to anextreme, and the central head end may send out no legacy QAM signalswhatsoever. This frees up a maximal amount of QAM channels forsubsequent neighborhood specific optimization.

In a third option, the virtual shelf system may instruct theD-CMRTS/DOFN units to reallocate their neighborhood CATV spectrum ormodulation scheme to allow for more upstream data to be transmitted. Forexample, the D-CMRTS units may work with various CATV cable connectedresidential gateways (See FIG. 10) to allocate a greater amount of CATVbandwidth to upstream data.

In either option, the virtual shelf system may instruct the head endGigE PHY (620) units to send neighborhood specific (IP/on-demand data)to those neighborhoods using optical fiber optimized digital datacarrying waveforms, such as GigE waveforms. The virtual shelf system maythen instruct the remote D-CMRTS unit on the fiber node serving thetarget neighborhood to take this IP/on-demand data, decode and QAMmodulate the data using local CMRTS devices (604), and inject this nowRF modulated QAM data on the cable for that particular neighborhoodusing the now empty QAM channels (frequency).

The virtual shelf system can also instruct another remote D-CMRTS uniton a different fiber node serving a different neighborhood to take theIP/on-demand data for this neighborhood from the massive amount ofdownstream GigE data, decode and QAM modulate this data and inject thisnow RF modulated QAM data on the cable for this neighborhood as well.

Note that by this method, even though both neighborhoods may optionally(for backward compatibility) receive some common legacy QAM channels anddata from the head end, the overall CATV QAM channels may not be thesame. Rather, at least for the IP/On-demand data, the same QAM channel(frequency) now carries different data for the two differentneighborhoods.

Using these systems and methods, the effective data carrying capacity ofthe various cables and QAM channels has been increased. Yet, at the sametime, if the centralized computer system (virtual shelf) is properlyconfigured, most of the complexity of this more advanced switchingarrangement can still be selectively hidden from both the upstream(cable head) and downstream (cable modem) systems, thus enabling goodbackward compatibility with existing HFC equipment.

Equipment needed to demodulate/digitize legacy signals:

As per Ser. No. 12/692,582, Ser. No. 13/675,936 and other discussions,incorporated herein by reference, in some embodiments, the system maywork essentially independently of the legacy CMTS or D-CMTS units at thecable head, and will essentially act to supplement the functionality ofprior art legacy equipment by adding a minimal amount of new equipmentat the cable head.

Here, this new equipment at the cable head cable may consist of variousdigital converters (399) that convert the legacy QAM, FM, QPSK waveformsfor digital output. Unit (399) in this embodiment should also beconsidered to have enough onboard computing functionality to extractthis data, subsequently package the data into the appropriate digitaloptical fiber data transport format, such as various Ethernet packets,and also to provide the fiber optic light source (e.g. one or moreoptical fiber laser transmitters) to transmit the digital optical fibersignals.

For more advanced functionality (e.g. Phase 3 functionality) otheroptional equipment may consist of a media Level 2/3 switch (629), avirtual shelf management system (622, 630), and appropriate MAC and PHYdevices to send and receive data along optical fibers.

In some embodiments, in order to facilitate the process of upgrading theDOFN from phase 1 to phase 2, phase 3 capability and beyond, it may beuseful to implement the DOFN using software configurable components(e.g. using FPGA and DSP components), as per the teaching of parentpatent application Ser. No. 13/555,170, the contents of which areincorporated herein by reference. In these embodiments, the HFC systemoperator need merely send appropriate configuration software over theoptical fiber to, for example, a phase 1 DOFN to reconfigure it forphase 2 capability, without the need for sending crews out into thefield to perform manual DOFN upgrades.

For more advanced functionality, in some embodiments, parts of thesystem may be embedded into an advanced D-CMTS (Digital Cable ModemTermination System) head (500) with at least a first packet switch, afirst MAC (Media Access Control), and a first PHY (Physical Layer) thatoptionally may be capable of sending and receiving data from a layer 2-3switch to a first end of a first optical fiber as at least a pluralityof first digitally encoded analog QAM waveforms (first optical signals).

In other embodiments, this first PHY (614) and MAC (612) may be omitted,and instead the D-CMTS head may instead use only a second MAC (618) anda second PHY (620) capable of sending and receiving data from the layer2-3 switch to the optical fiber.

As previously discussed, although in the preferred embodiment, all HFCoptical fiber signals will be sent in a digital format, the system canstill operate in a still higher backward compatible mode. Here abackward compatible wavelength, such as the standard HFC 1310 nmwavelength, may be reserved for prior art analog modulated optical fibersignals (e.g. QAM waveforms) (which may then be digitized for opticalfiber transmission by a converter unit). The invention's digital signalswill then operate on a different wavelength and a second head end PHYmay send and receive data from the IP backbone using this alternateoptical wavelength.

It will often be convenient to send both the legacy (digitized analogmodulated optical fiber signals) data and the advanced data usingsimilar digital protocols (e.g. various IP digital protocols such asGigE). This because then the same switches may be used to handle boththe legacy signals and the advanced functionality signals. This isbecause when all data flows using the same type of digital protocol, asthen simple switches can be used to send relevant data packets to therelevant destinations, and handle these data packets using theappropriate equipment once the data packets reach their intendeddestination.

As previously discussed, although in some embodiments, data may be sentand received using as many optical fiber wavelengths as desired, theinvention's digital optical fiber transmission techniques can reduce thenecessity for using multiple optical fiber wavelengths, and in turnreduce costs.

To help improve legacy HFC backward compatibility, the D-CMRTS/DOFNfiber node(s) may optionally incorporate one or more external “dumb”digital optical to RF (radio frequency) conversion devices (see FIG. 6,401) that directly convert the digitized versions of the prior artmodulated optical signals (sent as QAM waveforms by the CMTS PHY (614)at the first end of the fiber, then digitized by a converter (399), sentover the optical fiber digitally, and then reconstituted back to copiesof the original waveforms) to a first set of analog optical or RFsignals. These are typically designated as O-D/A-E or A-E/O-D (i.e.optical-digital to analog electronic, or analog electronic to opticaldigital) converters, depending upon the direction of the electrical RFto digital fiber optic conversion. Often, however this functionalitywill be incorporated into the D-CMRTS/DOFN nodes (e.g. 600, 601, 603,and 605).

In alternate and often more expensive (but higher performance)embodiments where the D-CMRTS/DOFN (300), (304) unit is designed tooperate at a plurality of different optical wavelengths, the units mayincorporate one or more wavelength splitting devices, such as Bragfilters, prisms, gratings, and the like as part of the unit's internalswitch (560), to separate and combine the various optical fiberwavelengths as desired. In some embodiments, these wavelength splittersmay be tunable wavelengths splitters that may operate under softwarecontrol. Although within the scope of the invention, such embodimentstend to be somewhat more expensive due to the costs of the extraequipment. Thus such multiple wavelength embodiments will typically beused more in very high (e.g. demanding) data transport situations.

The D-CMRTS may have at least one (and often a plurality of, e.g. asmany as 160 or more) CATV RF signal generators, such as QAM or OFDMmodulator devices. These devices will be capable of detecting andencoding selected portions of the digitally encoded optical fiber data(such as the underlying QAM or OFDM symbol data) into various types ofRF CATV waveforms. The device's switch (560) may, for example, be usedto sort out digitally sampled legacy RF signals, and send these to adigital-optical to analog-electrical (RF) converter (600), thusproducing copies of the original legacy RF signals. The switch may alsobe used to sort out demodulated legacy QAM signals (waveforms) whichcontain the underlying QAM symbols, and send these QAM symbols to QAMmodulators (603), thus producing copies of the original legacy RF QAMsymbols by another method. The switch may also be used to handle IP datapackets from the IP backbone connected to the head end, and send theseto appropriate QAM modulators (e.g. edge-QAM modulators 607 or 604).This later is particularly useful for various video on demand and DOCSISapplications.

The QAM or OFDM modulator(s) may be part of a D-CMRTS/DOFN PHY unit, andat least more advanced embodiments of the D-CMRTS/DOFN may often havethe corresponding MAC and packet switching capability, as well as anoptional controller (e.g. microprocessor and associated software) toselect the appropriate portions of the digitally modulated opticalsignals (and wavelengths if necessary) and also control the packetswitching, MAC and PHY (including the D-CMRTS QAM modulators) units asneeded.

More advanced embodiments of the D-CMRTS/DOFN will also usually containat least one software controllable switch that can be remotely directedto select at least some of the digitally encoded optical signals anddirect the at least one D-CMRTS QAM modulator devices to encode theselected optically transmitted digital data into various of RF QAMwaveforms at a selected set of frequencies (remotely generated QAMsignals). Often this software controllable switch will be part of, or becontrolled by, an optional processor or controller.

The D-CMRTS/DOFN may also contain at least one remotely softwarecontrollable RF packet processor capable of detecting upstream datacarried by CATV RF upstream signals generated by at least one cablemodem, and digitally repackaging and this upstream data and digitallyretransmitting this upstream data along the optical fiber.

The software controllable switch(s) and/or software controllable RFpacket processor(s) may optionally be capable of being remotelyconfigured by software to implement at least a subset of the standardDOCSIS upstream and downstream functions. For example, on the upstreamside, one or more of the DOCSIS upstream Time Division Multiple Access(TDMA) and DOCSIS Synchronous Code Division Multiple Access (SCDMA)functions may be implemented. On the downstream side, one or more of thevarious DOCSIS QAM modulation modes, such as 16-level, 32-level,64-level, 128-level, and 256-level QAM modulation modes may beimplemented. Depending upon the level of functionality of the D-CMRTSthat is desired, the D-CMRTS may, at the fiber node, generate QAMchannels carrying digital broadcast video, digital video on demand,digital High Definition (HD) video, Voice data, and DOCSIS (data)channels.

As previously discussed in Ser. No. 12/692,582, Ser. No. 13/674,936, andelsewhere, at least some embodiments of the CMRTS/DOFN units weredisclosed as being capable of implementing additional functions that arenot yet officially part of the DOCSIS specification (i.e. non-DOCSISfunctionality), such as upstream data from various new models ofnon-DOCSIS standard set-top box gateways, may also be implemented by theD-CMRTS/DOFN.

Here some of this optional non-standard functionality is discussed inmore detail. More advanced versions of the D-CMRTS/DOFN unit may beconfigured to implement additional functions that are not yet officiallypart of the DOCSIS specification (i.e. non-DOCSIS functionality). Thisadditional functionality can include ability to handle an increasedamount of upstream data from various new models of non-DOCSIS standardset-top box gateways. As another example, more advanced D-CMRTS/DOFNunits may be capable of more intelligently allocating the downstream QAMchannels depending upon data content need messages generated by moreadvanced set top boxes in various households. That is, if a householdneeds access to a particular video channel, for example, the household'sset top box may send a command to the local D-CMRTS/DOFN unit requestingthis channel. This channel may already be available to the D-CMRTS/DOFNunit because it has access to a vast stream of data from the opticalfiber connection, but in order to preserve scarce CATV bandwidth, thelocal D-CMRTS/DOFN unit will only allocate a CATV QAM channel for thisdata upon request. Other embodiments of the D-CMRTS/DOFN unit may alsobe capable of many other functions as well.

As another example, one persistent problem with CATV cable is that thesignal attenuation properties of the RF signals vary as a function offrequency, as well as the particular characteristics of that stretch ofcable. Lower frequency channels will degrade differently from higherfrequency channels. It is difficult, with the present “one size fitsall” scheme where all QAM channels at all frequencies are generated atthe cable head, to put out a standard CATV signal where all QAM channelsare modulated the same regardless of frequency. By contrast, since aD-CMRTS/DOFN unit may generate some or all RF channels (e.g. QAM RFchannels) locally, it is possible to use various software adjustableparameters to spectrally shape the various RF QAM waveforms to adjustfor the attenuation over frequency properties of the that neighborhood'sCATV cable. Thus in contrast to prior art methods, where often some ofthe lower or higher frequency channels have more noise, it will now bepossible to ensure that all channels have low noise, regardless of thefrequency of the channel.

Thus the present disclosure teaches methods that enable a cableprovider, over a series of gradual system upgrades as desired, toincreasingly be able to distinguish itself by being able to providecutting edge services that are ahead of its competitors. Various levelsof D-CMRTS/DOFN can be provided, from simple units designed for neartransparent upgrades of legacy HFC systems, to more advancedD-CMRTS/DOFN units that can handle either a superset of the DOCSISfunctions or a completely different set of functions, because it can beused to extend the functionality of the HFC system far beyond that ofthe standard DOCSIS functions.

Here the term “superset” is being used to denote the additional(non-standard DOCSIS) functionality. Thus, for example, a D-CMRTS/DOFNthat has enough backward compatibility to do either a full set of DOCSISfunctions or a subset of DOCSIS functions would be described asimplementing a DOCSIS “superset” if it also implements additionalnon-standard DOCSIS functions. Other examples of additional non-standardDOCSIS functionality (non-DOCSIS functionality) includes functionalityto transmit various forms of digital video such as standard digitalvideo, high definition HD digital video, and various forms of digitalvideo upon demand.

The various D-CMRTS/DOFN devices will usually have software controllableswitch(s) and software controllable RF packet processor(s), and willoften also incorporate their own microprocessors or microcontrollers, aswell as memory (such as flash memory, ROM, RAM, or other memory storagedevice) to incorporate software needed to operate the switches andprocessors, interpret command packets sent from the virtual shelfmanager, and transmit data packets to the virtual shelf manager.

For greater flexibility, the various D-CMRTS/DOFN devices may beconstructed using various software reconfigurable Field-programmablegate arrays (FPGA) and Digital signal processor (DSP) devices for theirvarious MAC and PHY units, as described in more detail in copendingapplication Ser. No. 13/555,170, “DISTRIBUTED CABLE MODEM TERMINATIONSYSTEM WITH SOFTWARE RECONFIGUABLE MAC AND PHY CAPABILITY”, the contentsof which are incorporated herein by reference. These FPGA and DSP unitsmay be software reconfigured to enable various types of QAM and othermodulation scheme transmitters and receivers, such as filter banktransmitters and filter bank receivers. These may be constructedfollowing the methods of Harris et. al., (“Digital Receivers andTransmitters Using Polyphase Filter Banks for Wireless Communications”,IEEE Transactions on Microwave Theory and Techniques, 51 (4), pages1395-1412, 2003). Other alternative methods may also be used.

The D-CMRTS/DOFN units will also often have an RF combiner device, or atleast be attached to a combiner device (such as a Diplex or Multiplexdevice), that combines all of the various RF QAM and other CATV signalsto produce a combined RF signal suitable for injection into a CATV cableconnected to at least one cable modem. The diplex or multiplex devicemay also serve as a frequency splitter, or an adjustable frequencysplitter, directing some frequency ranges (e.g. 5-42 MHz for upstreamfunctions, and other frequency ranges (e.g. 54-870 MHz) for downstreamfunctions. These frequency ranges may be adjusted under software controlas desired.

Alternatively, this multiplex device may be external to the actualD-CMRTS/DOFN unit; however the D-CMRTS unit will normally depend uponeither an internal or external combiner (e.g. a diplex or multiplexdevice) for functionality.

As previously discussed, although use with legacy HFC software is onebig advantage of the invention, when more advanced functionality isdesired, it can be implemented as well. To do this, often more advancedversions of the invention may additionally have a centralized computersystem or computer processor running software (e.g. virtual shelfsoftware) that controls many aspects of its function. As previouslydiscussed, because the prior art (non-dispersed functionally) CMTS unitswere often referred to as a “shelf”, the computer software that controlsthe functionality of the more advanced dispersed D-CMRTS/DOFN units ofthis invention will be referred to in the alternative as a “virtualshelf”. This “virtual shelf” software will ideally manage the muchhigher complexity of the dispersed D-CMRTS/DOFN system in a way thatwill be easy to manage, and ideally sometimes almost transparent, to thecable head, so that other systems in the cable head can often handle themore complex data distribution properties of the invention's dispersedD-CMTS-D-CMRTS system as if the system behaved more like a simpler,prior art, CMTS system.

For more advanced functionality, one important function of the computerprocessor and “virtual shelf” software will be to select and control atleast the digital optical signals and the remotely generated QAM signalsor OFDM signals. These can be managed in a way that, as will bediscussed, greatly increases the amount of IP-on-demand data availablefor cable system users.

FIG. 1 shows an overall view of the various frequencies and datachannels allocated for prior art CATV systems (100). Typically the lowerfrequencies, such as 5-42 MHz, were allocated for use in transmittingdata “upstream” from the individual cable modems back to the Cable Head(102). Typically upstream data was transmitted using a time-share TDMA(Time Division Multiple Access) manner in which individual cable modemsare allocated certain times on roughly 2 MHz wide QAM channels totransmit data. Starting at around 54 MHz on up to roughly 547 MHz, spacewas allocated for legacy analog video channels (104), which transmit onroughly 6 MHz wide FDM channels. At frequencies above that, frequencies(space, bandwidth) was allocated for digital television transmitting onroughly 6 MHz wide QAM channels (106), and above that, space wasallocated for DOCSIS services (108) that may transmit voice, on-demandvideo, IP, and other information, again generally as a series of 6 MHzwide QAM channels. Above about 1 GHz, cable bandwidth is and was seldomused, although future services may extend further into this region.

The invention is indifferent as to the use of higher frequency cablebandwidth and channels. If available, the invention may use them. If notavailable, the invention will cope with existing cable frequencies andbandwidth.

Prior art CATV cable thus had a finite bandwidth of at most about100-200 downstream QAM channels, and a very limited upstream bandwidth.When this bandwidth is used to serve a large amount of differentcustomized types of data to a large amount of different subscribers,this bandwidth quickly becomes exhausted. Due to the extreme constraintson upstream bandwidth, upstream bandwidth quickly became limiting.

A drawing showing how the prior art CATV spectrum allocation can bedescribed in a more simplified diagram is shown below (110), (120). Thisdiagram will be used in various figures to more clearly show some of theCATV spectrum allocation aspects of the invention, as well as to showhow the invention may deviate from the prior art CATV spectrumallocation on occasion.

The “upstream” segment (112) is an abstraction of all prior art CATVupstream channels, including both presently used upstream channels inthe 5-42 MHz region. The “video” segment (114) is an abstraction of boththe almost obsolete prior art analog TV FDM channels, as well as thestandard “digital video” channels, as well as the projected digitalvideo channels that will occupy the soon to be reclaimed analogbandwidths once the analog channels are phased out.

Segment (114) also represents other standard digital radio and FMchannels, and in general may represent any standardized set ofdownstream channels that will usually not be customized betweendifferent sets of users and neighborhoods.

The “DOC1” channel (116) may be (depending upon mode of use) either afull set or subset of present or future DOCSIS channels. As commonlyused in this specification, DOC1 often represents a basic set of DOCSISservices that would be made available for fallback use by neighborhoodsin the event of a failure of the higher performance IP/on demand or DOC2channels (118). The DOC1 QAM channels are normally chosen so as to notexhaust the full bandwidth of the CATV cable, so that at least someremaining QAM channels are available for the neighborhood customizedDOC2 channels. The “IP/On-demand or DOC2” channel (118) is essentially(depending upon mode of use) the remaining available downstreambandwidth on the CATV cable, and is usually reserved for transmittingneighborhood specific data (IP/On-demand data), often transported by adifferent communications media (such as a second fiber or secondwavelength, and often by a non-QAM protocol) from the cable head toindividual neighborhoods.

Note that when discussing prior art usage, the sum of the DOC1 (116) andIP/On demand (118) channels sent by optical fiber to a group ofneighborhoods can never (or at least should not ever to avoidinterference) exceed the effective bandwidth (i.e. the carrying abilityof the CATV cable and the ability of cable modems to detect the cable RFsignal) of the CATV cable.

By contrast, when discussing the invention, the sum of the DOC1 (116)and IP/On-demand (118) channels sent by optical fiber to a group ofneighborhoods will often exceed the effective bandwidth of the CATVcable on a group of neighborhoods basis, although the sum of DOC1 (116)and IP/On-demand (118) RF waveforms or signals will never exceed theeffective bandwidth of the CATV cable on a per-neighborhood basis.

If the same CATV spectrum is transmitted by optical methods (i.e.optical fiber), so that the same waveforms are transmitted at the samefrequency spacing, but simply transposed to optical wavelengths, thenthis spectrum will be designated as (120), but the various waveformswill otherwise keep the same nomenclature to minimize confusion.

Some embodiments, the invention may also intentionally deviate from thisprior art CATV spectrum allocation scheme. In particular, as will bediscussed, the amount of bandwidth reserved for upstream data may besubstantially increased. This may be done by, for example, deviatingfrom the traditional 4-42 MHz region reserved for upstream data, andallocating a larger number of CATV RF frequencies for upstream data.

FIG. 2 shows an overall view of the various wavelengths allocated forboth prior art optical fiber wavelength division multiplexing schemes,as compared to the dense wavelength division multiplexing (DWDM) methodswhich may optionally be used in some embodiments of the presentinvention. Here the optical fiber wavelengths being used at present(150) include a 1310 nm O-band wavelength (152) often used to transmitthe various CATV RF channels, such as the various QAM channels,modulated essentially according to the same CATV RF waveforms, but atoptical wavelengths according to scheme (120). Supplemental data isoften transmitted in the C-band around 1550 nm (154), often on opticalwavelengths and waveforms that, because the waveforms are modulatedaccording to non-optimal CATV waveforms, must be separated from eachother by a relatively large wavelength separation, and which carrysub-optimal amounts of data per wavelength.

By contrast, if all data is transmitted according to the same digitalformat, such as an IP based GigE format, then it becomes relativelysimple to label any type of data as to data type and data destination,dump it in the optical fiber digital stream at the same opticalwavelength (170), and then extract the digital data at the other end ofthe optical fiber, sort by data type and destination, and send it to theproper recipient. This all digital approach thus can have substantialadvantages over DWDM methods because the DWDM costs of producing opticalmodulators (e.g. optical fiber lasers) as well as demodulators,wavelength splitters, and the like, thus can be reduced.

Although the present invention, by virtue of the fact that all data willusually be transmitted digital form over the optical fiber, thus doesnot require use of dense wavelength division multiplexing (DWDM)methods, it is useful to briefly examine such DWDM methods because theymake the advantages of the present invention's all digital approach moreapparent.

The Dense Wavelength Division Multiplexing (DWDM) concept is shown in(160), and is discussed in more detail by way of copending applicationSer. No. 13/555,170 and provisional applications 61/385,125 and61/511,395, the contents of which are incorporated herein by reference.These applications taught that backward compatible downstream legacysignals might be transmitted in analog form using, for example, a legacyO-band analog signal, and additional channels and services might betransmitted at multiple wavelengths using more efficiently modulateddata signals (such as one of the various optical fiber GigE protocols),for example as a series of closely spaced wavelengths (162). Theseprovisional applications also taught that due to the fact that becauseuse of prior art QAM, NTSC, FM waveforms and the like, when used onoptical fiber, is relatively inefficient, on a bits of data per unitbandwidth basis, compared to more modern digital methods of transmittingdata, use of digital signal transmission methods offered compellingdifferences in data transmission rates.

Specifically, whereas prior QAM, NTSC, FM waveform methods might, forexample, be used to transmit 4 C-band wavelengths, each carrying about 6gigabits per second of data, using CATV compatible QAM, NTSC, FMwaveforms (154), by switching to digital methods, much higher datarates, such as up to 80 wavelengths of C-band data (162), each carrying10-100 gigabits of data per second, are possible using more efficientoptical fiber signal modulation methods.

The present invention thus builds on this earlier insight, and is basedon the further insight that by completely digitizing all optical fibertraffic (e.g. removing the legacy analog waveform optical fibertraffic), intelligently compressing as possible (e.g. using QAM symboldemodulation methods) and going all digital, then on a bits per secondbasis, much more data may be transmitted using fewer opticalwavelengths, thus saving the costs of the extra equipment needed tohandle the extra optical wavelengths.

Note however that the present invention still may make use of DWDMmethods when, for example, extremely high data transmission rates (bitsper second) are desired. However in the present invention, use of alldigital optical fiber transmission is now the preferred embodiment, anduse of DWDM methods is an optional element that is not required topractice the invention, although it may be.

To help visualize how switching to an all digital optical fibertransport format can help transmit more data over even a single opticalfiber wavelength, the simplified digital transmission diagram (170) or(306) is frequently used. Note that a legacy O band analog modulatedoptical signals (152) or C band optical signals (154) can carry only atmost about 6 Gigabits per second (Gbit/s), with an effective bit ratemuch less than this due to the inefficiencies of the analog format. Bycontrast, the more efficient digital format can transmit 10, 40, 100,1000 or more Gbits/second or more at the same wavelength, and here theeffective bit rate is very close to the theoretical bit rate. The neteffect is that by switching to an all digital mode, the same wavelengthon the optical fiber can now transmit much more data than it couldearlier.

FIG. 3 shows a simplified version of how prior art HFC systems (200)transmit data from the cable head (202) to different optical fiber nodes(204) serving different neighborhoods (206). Each neighborhood willtypically consist of up to several hundred different houses, apartments,offices or stores (208) (here referred to generically as “houses”), eachequipped with their own cable modems (not shown). Here, for simplicity,only the downstream portion of the HFC system is shown.

The cable head will generally be connected to an IP backbone (212)and/or will obtain standardized media content (210) (such as a standardassortment of analog and digital video channels) from one set ofsources, and also obtain more individualized data (212), such as videoon demand, IP from the IP backbone which may include both the internet,and other individualized data from other sources. This data is compiledinto a large number of different QAM (and at present also FDM) modulatedCATV broadcast channels at (214). The CMTS shelf, shown here also (214)will often have a number of different blade-like line cards (216) Thevarious QAM channels and IP data are combined and are transmitted byoptical fibers (218) to different areas (groups of neighborhoods).

Note that the FDM modulated CATV broadcast signal is an NTSC analogsignal (for older style analog televisions), and even the QAM signal,although it carries digitally encoded information, is itself an analogsignal as well. For historical reasons, in the downstream direction,both FDM/NTSC and QAM waveforms (signals) usually have a bandwidth ofabout 6 MHz in the US.

To show this, as previously discussed in FIG. 1, the FDM/NTSC and QAMsignals are shown as having a center wavelength and bandwidth in orderto emphasize the essentially analog nature of this signal, even whencarrying digital information. These analog signals can be carried byoptical fibers, and converted into RF signals for the CATV cable part ofthe network, using very simple and inexpensive equipment.

As previously discussed, typical HFC networks actually have a rathercomplex topology. Rather than sending one optical fiber from the CTMS toeach different neighborhood, typically optical fibers will servemultiple neighborhoods. To do this, the signal from the CTMS sideoptical fiber will at least usually be split (by an optical fibersplitter (220)) into several different optical sub-fibers (222), andeach sub-fiber in turn will in turn carry the signal to a differentfiber optic node (fiber node, FN) (204). Here the rather complex ringtopology of HFC networks will be simplified and instead represented bythese fiber splitters.

At the fiber node (FN) (204), the optical signal is converted into aCATV radio frequency (RF) signal and sent via CATV cables (226) toindividual cable modems at individual houses (208) in each neighborhood.Typically each neighborhood will consist of 25 to several hundredhouses, served by a CATV cable (226) that connects to the local fibernode (204).

Since the CATV cable (226) is connected to all of the houses (208) inthe neighborhood (206), if the cable modem in one house in aneighborhood wants to request customized on-demand video or IP, then allof the houses in the neighborhood that are attached to that particularCATV cable will actually receive the customized signal. Although onlythe cable modem associated with the requesting house (not shown) willactually tune into and decode the requested signal, it should beappreciated that if each individual house in the neighborhood were tosimultaneously request its own customized set of video on demand or IPat the same time, the limited bandwidth of the CATV cable would berapidly saturated. As a result, there is an upper end to the amount ofcustomized data that can be transmitted to each house, beyond whichbandwidth must be limited and/or requests for additional customized datawill have to be denied.

Although the different blades or line cards (216) of the CMTS shelf(214) at the cable head (202) can send different customized IP/on-demandchannels to different groups of neighborhoods, the granularity of thisprocess is sub-optimal, because all individual neighborhoods connectedto the same fiber splitter will get the same customized IP/on-demandsignal. Given the limited bandwidth of the CATV cable, if allneighborhoods get the same signal, then the amount of data that can besent to each individual neighborhood must, by necessity, be limited soas not to exceed the total available bandwidth.

FIG. 4A shows an overview of how the invention may be used to upgrade alegacy analog optical fiber (222) based HFC CATV cable system byreplacing the analog modulators (201) and demodulators (300) on eitherend of the system with digital demodulators (399) and remodulators(300), where here the remodulators are generally embedded into the DOFN(300) as the various QAM modulators (712) and the like. The DOFN areconnected to the optical fiber (222) on one side, and the neighborhoodCATV cable system (226) on the other side. The neighborhood CATV systemin turn connects to various households (208) as before, and also maycontain various active devices (290) such as amplifiers to boost the RFsignals, and the like. The head end of the CATV system (202) is hereabstracted as a device that generates a plurality of downstream RFwaveforms/signals, such as QAM signals (106).

FIG. 4B shows a more detailed overview of how the invention may be usedto upgrade a legacy analog optical fiber based HFC CATV cable systemthat is was transmitting a mixture of consisting of a plurality of videoQAM channels (106) and IP data (108), such as DOCSIS IP data. Here thelegacy QAM channels (106) may be demodulated into their underlying QAMconstellation symbols by converter device (399). This QAM symbol data,along with the legacy IP data (108), can be encapsulated by theconverter device (399) into various digital optical data packets, andtransmitted over the optical fiber (222) in this more efficient digitalform. At the optical fiber node (300 a), the data packets can be parsed,and the QAM or other RF channels regenerated by remodulated by using theQAM constellation symbols or OFDM symbols to drive various optical fibernode QAM RF modulators/transmitters, such as (712). The IP data can alsobe extracted from the optical data packets, and used to feed an opticalfiber node based CMTS system.

In this context, “encapsulate” means to package the data bits, bytes, orother bit oriented format from the relevant input into data packets,such as Ethernet data packets or frames, along with appropriate headers,checksums, source information, destination information, and otherappropriate control information. Thus using QAM waveforms as an example,the data will be QAM constellation symbols, usually as part of theEthernet frame/packet payload. In addition to standard Ethernet framestructure data, this payload data may additionally contain informationabout the relative position or timing that the QAM symbols have in theQAM waveform, the source of the QAM waveform (e.g. what channel), thedestination channel, and even information as to intensity of the QAMwaveform, QAM waveform pre-distortion, echo cancellation, and the likeas needed to help correct for distortions in the CATV cable, as percopending patent applications Ser. No. 13/400,415 and Ser. No.13/478,461, the contents of which are incorporated herein by reference.Once the data packets are received, the QAM symbol data or other datacan be extracted, and the source information, destination information,and other appropriate control information then used by the system tothen properly use the QAM symbol data to accurately reconstruct theproper QAM waveforms or other type waveforms as is best suited for theuse at hand.

Thus one important application of the invention is to provide a methodof upgrading a legacy Hybrid Fiber Cable (legacy HFC) system, previouslyconfigured to transmit data downstream over an optical fiber usinganalog optical QAM waveforms, to a digital HFC system configured totransmit data downstream over the optical fiber using digital opticaltransmission methods. Here, as previously discussed, the legacy HFCsystem will generally comprise a head end configured to producedownstream RF QAM waveforms, and a legacy fiber optic transmitter systemconfigured to transduce the RF QAM waveforms into downstream analogoptical QAM waveforms to be transmitted downstream to at least onelegacy optical fiber node. The legacy HFC system will also generallycomprise at least one legacy optical fiber node is configured to receivethe downstream analog optical QAM waveforms, transduce the analogoptical QAM waveforms into RF QAM waveforms, and transmit these RF QAMwaveforms downstream over the at least one set of neighborhood CATVcables.

To upgrade this system, the legacy fiber optic transmitter system (201),which is generally attached in between the CATV PHY (614) and theoptical fiber cable (218), can be replaced with a digital fiber optictransmitter system (399) configured to transmit at least one downstreamQAM channel over the optical fiber as a plurality of QAM constellationsymbols by demodulating the QAM waveforms, extracting the QAMconstellation symbols encapsulating the QAM constellation symbols into aplurality of Ethernet frames or other digital transmission formatframes, and digitally transmitting this plurality of Ethernet frames orother digital transmission format frames over the optical fiber.

The conversion will also generally require that at least one legacyfiber optic node (204) be replaced with a digital optical fiber node(DOFN) (300) configured to receive this plurality of Ethernet frames orother digital transmission format claims, extract these downstream QAMconstellation symbols, and use these downstream video QAM constellationsymbols to modulate at least one DOFN QAM modulator, thus producingdownstream QAM RF signals.

Here the downstream QAM channels will generally comprise either videoQAM channels, video Edge-QAM channels, or IP-QAM channels.

In some cases, as described in more detail elsewhere the downstream datamay further comprise either legacy RF waveforms, such as NationalTelevision System Committee (NTSC) or more advanced DOCSIS 3.1waveforms, such as Orthogonal Frequency Division Multiplexing (OFDM) RFchannels. In these situations, the system may further handle thesenon-QAM signals by, for example:

1: digitally sampling the NTSC or OFDM RF channels at the head end,producing a plurality of digitized waveform data, encapsulating thisdigitized waveform data into a plurality of digitized waveform datacontaining Ethernet frames or other digital transmission frames, anddigitally transmitting this plurality of digitized waveform datacontaining Ethernet frames or other digital transmission framesdownstream over the optical fiber (222). There, at the DOFN (300), thesystem may receive this plurality of digitized waveform data containingEthernet frames or other digital transmission frames, extract thisplurality of digitized waveform data, and use this plurality ofdigitized waveform data to drive at least one digital to analogconverter, thus producing downstream NTSC or OFDM RF channels which inturn can be injected into the neighborhood CATV cables (226).

In the case where the downstream data may be composed of more advanced(e.g. DOCSIS 3.1) Orthogonal Frequency Division Multiplexing (OFDM) RFchannels, these OFDM RF channels may be digitally transmitted bydemodulating the OFDM RF channels at the head end (399), producing aplurality of OFDM symbols, encapsulating this plurality of OFDM symbolsinto a plurality of OFDM symbol carrying Ethernet frames or otherdigital transmission frames, and digitally transmitting these OFDMsymbol carrying Ethernet frames or other digital transmission framesdownstream over the optical fiber (222).

In this case, the DOFN (300) can be configured to receive this pluralityof OFDM symbol carrying Ethernet frames or other digital transmissionframes, extract this plurality of OFDM symbols, and use this pluralityof OFDM symbols to drive at least one OFDM RF modulator, thus producingdownstream OFDM RF channels, and also inject these OFDM RF channels intothe local neighborhood CATV cable system (226) as well.

In this approach, the upstream transmission methods generally areconsistent with the above discussed downstream methods. Here, forexample, when upstream transmission of RF QAM channel data waveforms orany upstream RF channel data waveforms or desired, the DOFN (300) or(300 a) may be configured to, for the case of upstream RF QAM datacarrying waveforms, receive the upstream RF QAM channel waveforms,demodulate these upstream RF QAM channel waveforms into a plurality ofupstream QAM constellation symbols, and encapsulate this plurality ofupstream QAM constellation symbols into a plurality of Ethernet framesor other digital transmission format frames. The DOFN (300), (300 a) canthen use the optical fiber (222) to digitally transmit this plurality ofEthernet frames or other digital transmission format frames upstream thehead end (399). Similarly for upstream RF OFDM channel data, the DOFN(300), (300 a) can be configured to receive the upstream RF OFDM channeldata waveforms, and demodulate the RF OFDM channel waveforms into aplurality of upstream OFDM symbols. The DOFN can then encapsulate thisplurality of upstream OFDM symbols into a plurality of Ethernet framesor other digital transmission format frames and transmit upstream onoptical fiber (222) as described previously.

In the case where the upstream data are other types of RF waveforms (orwhere desired for QAM and OFDM upstream waveforms as well), as anotheralternative, the DOFN can be configured to receive the upstream RFchannel data waveforms, and digitally sample these RF channel datawaveforms producing a plurality of digitized waveform data. Then asbefore, the DOFN can encapsulate this digitized waveform data into aplurality of Ethernet frames or other digital transmission frames, andtransmit upstream on fiber (222) to the head end as before.

The process of migrating from a legacy analog-signal over optical fiberHFC CATV system to an improved digital signal over optical fiber HFCCATV system can take place in various phases or increments. At thesimplest upgrade phase or increment, here called phase 1, any prior artDOCSIS and CMTS functionality can be left intact, and only the video QAMwaveforms sent downstream over the optical fiber from the head end tothe various optical fiber nodes needs to be demodulated into QAMconstellation symbols, encapsulated or packaged into suitable digitaloptical packets such as various Ethernet packets, and sent downstream toimproved DOFN optical fiber nodes that in turn can extract the variousQAM constellation symbols from the digital optical fiber data packets.These DOFN fiber nodes can then use these QAM constellation symbols,together with various DOFN QAM modulators, to reconstruct the originalhead end QAM waveforms as RF QAM waveforms, and then send thesedownstream over the local neighborhood CATV cable.

In a preferred upgrade phase or increment, here called phase 2, both thedemodulated QAM constellation symbols from the various video QAMchannels and the various IP data (e.g. DOCSIS IP data, originating fromhead end CMTS units) can be encapsulated or packaged into suitabledigital optical packets, and be sent downstream over the optical fiber.The DOFN will also preferably be configured to return any upstream dataover the optical fiber using digital protocols as well.

In a still later upgrade phase or increment, here called phase 3, thecable head end need no longer be configured to generate QAM RFwaveforms. Instead, the cable head end can be still further simplified,and can for example translate video data directly into digital data,such as QAM symbol data, but head end QAM modulators are no longerneeded. Instead the cable head end can be essentially “all IP” or alldigital. One advantages of the methods described herein is that the DOFNneeded to implement phase 1 or phase 2 of the upgrade can still be usedfor the phase 3 upgrades as well, thus enabling the upgrade process toproceed in various incremental steps as budgets and user needs dictate.

Upgrading from an analog optical fiber system to a digital optical fibersystem has numerous advantages. In addition to the advantages discussedelsewhere in the specification, there are other advantages as well.

In contrast to analog transmission, which requires high linearitycomponents and signal transmission methods, and where at every signalcombining step, (which generally also requires an amplification step aswell) the noise floor level of the analog signal will generally rise,digital methods are generally superior:

1: Digital signal transmission methods can generally avoid non-linearityartifacts, such as cross-talk, that can corrupt signals.

2: Digital methods generally operate with a lower noise floor.

3: Digital methods generally produce higher level signals with improvedsignal to noise rations.

Particularly for optical fiber methods, where lasers used to transmit orto drive the optical fiber signals have limitations, such a requirementthat the laser not be overdriven. Thus to avoid this, the various analogwaveforms are driven at a lower intensity, and thus at varioussubsequent steps such as upon being the optical signal being receivedand demodulated, further amplification is needed, which in turnincreases the noise floor still further. By contrast, various digitalsignal protocols optimized for optical fiber can avoid these effects.

As a result, by switching to using digital signal transmission protocolsover optical fiber, the overall power requirements of the system canalso be reduced. The optical fiber lasers don't need to be operated inas high a linearity mode, and thus can be biased with a smaller amountof current, reducing transmitter power utilization. Further the need forpower amplifiers, which often add about 10-12 watts of power utilizationper amplifier, is also reduced. Thus in addition to the advantages ofhigher data throughput and more flexibility discussed elsewhere in thisspecification, there are also advantages of lower power utilization, andlower noise levels (i.e. less digital signal corruption due to noise).

Various optical fiber digital transport protocols may be used for suchdigital over optical fiber transmission purposes. In some embodiments,it may be useful to select a protocol from the set of various IEEE 802.3high speed Ethernet protocols, such as IEEE 802.3ba, IEEE 802.3bm, IEEE802.3bg, IEEE 803.3z and the like. Here, depending on the legacy opticalfiber in use, longer distance capable single-mode optical fiber (SMF)methods, such as 40GBase-LR4, 100GBase-LR4, or 100Gbase-ER4, 1000Base-X,1000Base-SX, 1000Base-LX, 1000Base-LX10, 1000Base-EX, 1000Base-ZX,1000Base-BX10 and other methods may also be used. If the legacy analogoptical fiber is going to be used without substantial upgrades, then useof digital protocols that are compatible with the wavelengths used bythe analog optical fiber, such as commonly used 1310 nanometer legacy Oband wavelengths (e.g. 1000Base-LX, 1000Base-LX10 or 1000Base-EX) may bepreferable. If use of alternative wavelengths, such as the C bandwavelengths (e.g. 1550 nanometer wavelength) are preferred, then use ofalternative protocols such as 1000Base-ZX may be preferable. Many otherprotocols, such as 1000Base-BX10 may also be used.

FIG. 4C shows still more detailed of how the invention may be used toupgrade a legacy analog optical fiber based HFC CATV cable system thatis was transmitting a mixture of consisting of a plurality of legacyvideo QAM channels, other analog RF channels such legacy NTSC videochannels, and legacy IP data, such as DOCSIS IP data. Here, a number ofthe various components are further identified using the nomenclatureused for FIG. 7, and it may be useful at this time to compare FIG. 4C toFIG. 7, since the two figures are highly related.

Here, as before, the legacy video QAM channels (106) may be demodulatedinto their underlying QAM constellation symbols using a demodulatordevice in converter unit (here 399 b). The other RF video channels (104)may be handled by digitization and optional compression, as desired,using appropriate analog to digital converter circuitry in converterunit (399). OFDM RF channels may also be handled by suitabledemodulators or digitizers, as desired (not shown). This QAM symboldata, digitized RF channel data and the legacy IP data, can beencapsulated into various digital optical data packets, and transmittedover the optical fiber (222). At the DOFN optical fiber node (here shownas 300 b and also as 304) the data packets can be parsed (560), and theQAM channels regenerated or remodulated by using the QAM constellationsymbols to drive various optical fiber node QAM RFmodulator/transmitters (603). The digized analog RF channels (which canoptionally be decompressed) are reconstituted by feeding them into anelectrical system comprising a digital to analog converter (600) toregenerate the analog RF channels. The IP data signals are selected andconverted in to the appropriate CATV waveforms by the DOFN's CMTS/CMRTSunit. The three types of RF waveforms can then be combined (606) andinjected into the neighborhood CATV cable system (226) as before.

FIG. 4D contrasts the difference in downstream data transmission betweena prior art HFC system that operates using an optical fiber carrying ananalog CATV modulated 1310 nm wavelength signal, and the invention'simproved digital methods using digital (Ethernet) modulated signals orother optical fiber optimized digital signal formats.

In the prior art system, the conversion process between the opticalfiber (222) and the CATV cable (226) that occurs with a typical priorart fiber node (204) is shown, and contrasted with the invention'simproved D-CMRTS fiber node (300). Here, for simplicity, only thedownstream portion of the process is illustrated.

In the prior art conversion process (top), the optical fiber (222)carries both the standardized video signals, and the analog QAM signal(that contains digital information) for both digital television andDOCSIS use (that can carry on demand video or IP data).

The prior art “dumb” fiber node (204) simply converts the opticalfiber's optical FDM or QAM analog signals into RF FDM or QAM signals andpasses these signals to the CATV cable (226). Thus if, for example,there are four different CATV cables connecting to this different fibernode, all will get the same customized IP/On-demand signal, and this inturn may be rather inefficiently transmitted to potentially thousands ofnon-target households that did not request the customized signal.

By contrast, by using the invention's improved “smart” D-CMRTS/DOFNfiber nodes (300), any legacy standardized signal (e.g. the standardizedvideo channels) and (for backwards compatibility) either a full set orsubset of the DOCSIS QAM channels are first digitized and transmitted bythe optical fiber in a digital format. This digital format makes it easyto add additional (non-legacy) data (e.g. video on the demand, DOCSISsuperset services) and transmit this additional data on the same opticalfiber wavelengths used to transmit any legacy CATV data.

If legacy data is transmitted over the optical fiber, it may optionallycarry a digitally encoded version of the legacy CATV spectrum, which canbe reconstituted (320) into analog format at the D-CMRTS unit into RFQAM waveforms and other waveforms that may optionally be injected intothe CATV cable (120) for fallback or legacy operation.

To emphasize the fact that the optical fiber is often carrying data bynon-CATV-compatible or QAM signal carrying methods, the signal carriedby the D-CMRTS fiber is shown as a series of lines (306) to symbolizethe fact, that alternative digital (e.g. GigE) methods of signaltransmission are being used. Here each line (306) represents a differenttype of data stream to different node addresses or different nodechannels or CATV waveforms, some of which will ultimately will beconverted to a QAM signal and sent to a specific neighborhood.

At the invention's improved D-CMRTS/DOFN fiber node (300), in moreadvanced embodiments, the fiber node's CMRTS unit may additionallydetermine (or at least select) which set of customized data carried bythe various optical fiber digital packets (307, 308, 310, 312) isintended for that particular D-CMRTS and neighborhood, and retrieve thisinformation from the fiber. This information will then be QAM modulatedand converted to the appropriate RF frequency, put onto a suitable emptyIP/On-demand QAM CATV cable channel (314), (316), (318), and then sentby CATV cable to the neighborhood that requested that particular data.At the neighborhood, the particular cable modem from the house thatrequested that data can tune into this QAM channel and extract the data,while the other cable modems also attached to that cable will ignore theQAM channel and/or ignore the data.

As can be seen, the digital data packets (306) carrying different typesof data can be selected and put onto the CATV cable in various mix andmatch combinations (316), (318) as desired. Here for example, one RF QAMchannel on (316) came from optical fiber data packet type (310), two RFQAM channels came from optical fiber data packet type (312), and one RFQAM channel came optical fiber data packet type (308). By contrast, for(318), two RF QAM channels came from optical fiber data packet type(310), one RF QAM channel came from optical fiber data packet type(308), and one RF QAM channel came from optical fiber data type (312).By contrast, (314) illustrates the CATV channel coming from aneighborhood that is operating in legacy mode, where all channels camefrom optical fiber data packets from digitally sampled or demodulated(320) legacy RF signals (120) that were simply transported, in digitalformat, as is and then reconstituted (320) back to the originalwaveforms at the D-CMRTS fiber node (300), or alternatively by a simpleroptical digital to RF analog converter type optical fiber node.

As will be discussed shortly, this method allows for much finergranularity, and a correspondingly higher rate of transmission ofcustomized data.

As previously discussed, in more advanced embodiments, the upstream datatransmission bottleneck at the CATV cable may be also addressed by anupstream CATV bandwidth reallocation scheme (See FIG. 10, (390)). Here,the amount of CATV RF spectrum allocated to upstream data transmissionmay, for example, be increased—e.g. from the original 5-42 MHz range upto, for example, 5-547 MHz or other higher upper value.

FIG. 5 shows an overview of one embodiment of the invention in operationin downstream mode. Here, in this embodiment, the improved “smart”D-CMRTS/DOFN fiber nodes (300) can transport a higher effective amountof customized user data. Here these improved “smart” D-CMRTS/DOFN fibernodes (300), may in some embodiments, work in conjunction with anoptional improved D-CMTS shelf and improved D-CMTS line cards at thecable head (see FIG. 7, 500).

In this embodiment, any legacy CATV RF waveforms, such as QAM waveforms(120), produced at the head end (202) may be digitized by a converterunit (399) and then injected into the optical fiber (301). Thisconverter unit (399) may function by, for example, being configured toaccept at least one of downstream RF waveforms and downstream QAMchannels from the head end, sample and digitize the downstream RFwaveforms (e.g. using simple high speed analog to digital conversion)and/or demodulate the downstream QAM channels into QAM symbols,producing downstream digital QAM symbols. In this embodiment, theconverter (399) is then digitally encoding the digitized legacy datainto a suitable optical fiber digital transport format, such as GigEdata packets, and then injecting these data packets into optical fiber(301) along with other data.

In the prior art system example previously shown in FIG. 3, an opticalfiber (218) from the prior art CMTS unit (214) at the cable head wassplit at by a fiber splitter (220) into three sub-optical fibers (allcarrying the same data) (222), and these sub-optical fibers were thenrouted to three different neighborhoods. Because all optical fiberscoming from the fiber splitter will carry the same data, all data,including customized data, is inefficiently sent to all threeneighborhoods, even though only one house from one neighborhood may haveactually requested the customized data.

As a result, the limited carrying capacity (bandwidth) of the prior artCATV cable system rapidly becomes saturated.

By contrast, by using an improved head end D-CMTS shelf (500) withimproved D-CMTS line cards, and the present invention's digitaltransmission methods, larger amounts of downstream data can be sent evenwhile using the same number of prior art optical fiber wavelengths.Again, the key concept is to use more efficiently modulated opticalfiber digital data transport protocols, such as higher data capacityGigE modulation protocols (304).

On the way to the various neighborhoods, or at the variousneighborhoods, the optical fiber cable and/or CATV cable data signalsmay optionally pass through a digital switch (220D). Here theinvention's present use of all digital transmission methods providesadvantages over the previously proposed DWDM methods.

Under DWDM methods, data to different optical fiber nodes, or multipleoptical fiber node devices, might be transmitted at differentwavelengths, requiring that the switch (220) be a smart fiber splitterthat might, for example, incorporate rather expensive optical devices,such as software controllable Brag filters, that would operate toseparate out the various optical fiber wavelengths and divert them todifferent neighborhoods as needed.

By contrast, by using digital transport methods, digital switch (220D)can be a relatively inexpensive multiple port switch that operates todirect the various digital data packets to their respective destinationsaccording to digital data packet headers, and the like.

To do this, typically the various DOFN or D-CMRTS units will have aprocessor, memory, and at least one address (e.g. the specific nodeaddress, and or one or more alternate addresses such as the address of agroup of nodes, useful for when broadcasting the same signal to multiplenodes is desired). The DOFN or D-CMRTS units will typically beconfigured to process downstream digital data that is directed to theirrespective addresses.

Here, also, the IP data packets (e.g. digital samples of downstream RFwaveforms, downstream digital QAM symbols, or downstream digital IPdata) transmitted over the optical fiber will often have a specific(e.g. individual node or group of nodes) digital optical fiber nodeaddress.

In some embodiments, digital switch (220D) may be a multiple port switchdisposed either at the head end or else somewhere between the head endand the various digital optical fiber nodes (D-CMRTS units). This switch(220D) can thus be configured to read the specific digital optical fibernode or D-CMRTS addresses; and direct any of the various digital samplesof downstream RF waveforms, downstream digital QAM symbols, ordownstream digital IP data to the specific digital optical fiber node ornodes corresponding to their specific digital optical fiber nodeaddress, be it individual node address, or specific group of nodesaddress.

Here, use of all digital methods also helps cost reduce the variousD-CMRTS/DOFN costs. Whereas under the prior DWDM scheme, the variousD-CMRTS units themselves may have extracted data from multiple opticalfiber wavelengths through use of more expensive wavelength splitters(such as software controllable Brag filters), use of digital datapackets makes use of such wavelength splitters optional. Under thepresent all digital scheme, the various D-CMRTS units can essentiallypick and choose what GigE formatted data they may need from the overalldigital data packet stream (306, 307, 308, 310, 312) extract this data,reconstitute, remodulate, or QAM modulate the various data types, andthen output CATV RF signals (again often QAM channels) that can be acomposite of the data originally carried on the different digital datastreams (307, 308, 310, 312).

This “mix and match” process is symbolized by the various dark, dashed,and dotted parabolas shown in (316) and (318), which symbolize the CATVRF modulated data that is being output in neighborhood 1 andneighborhood 2 by D-CMRTS Fiber Node 1 and DCMRTS Fiber Node 2. Here forexample, as before, the downstream CATV data (226), (316) onneighborhood 1 is shown as a mix of dark parabolas (data originallyobtained from fiber digital data packets (310), a mix of dashedparabolas (data originally obtained from fiber digital data packets308), and dark dotted parabolas (data originally obtained from fiberdigital data packets 312). Note that the mix of data for neighborhood 2(318) is different from neighborhood 1. Whereas neighborhood 1 only tooka small amount of data (dark parabola) from fiber digital data packets(310), and a larger amount of data (two dark dotted parabola) from fiberdigital data packets (312), here the D-CMRTS/DOFN unit (300) forneighborhood 2 has selected more data (two dark parabolas) from fiberdigital data packets (310), and less data from (one dark dottedparabola) from fiber digital data packets (310).

Note also that the D-CMRTS/DOFN unit has freedom to decide whatfrequencies will be used to transmit this data over the CATV cables.Here the D-CMRTS/DOFN units determine what data to place on theneighborhood CATV cables based upon commands sent upstream by thevarious household devices attached to the CATV cable, and/or commandssent from the cable head. As previously discussed, in more advancedembodiments the D-CMRTS/DOFJ optical fiber nodes will be softwarecontrolled.

In more advanced embodiments, due to this software controllable,neighborhood specific (or at least neighborhood region specific) abilityto combine and repackage huge amounts of GigE formatted data carriedover a large number of optical fiber channels, the downstream capabilityof the system can now be substantially higher than prior art HFCsystems.

Note also that some backward compatibility can be preserved, if desired.Here, for example, fiber digital data packets (307) can still be used todigitally transmit the legacy CATV RF signals, such as QAM signals. Thiscan be done by having converter (399) intercept the legacy signals,digitize them by relatively simple Analog-RF to Digital Optical units,or by demodulating the QAM waveforms, extracting the QAM symbols, andthen transmitting the QAM symbols in a digital format.

These digitized legacy signals can continue to be sent to “dumb” or“legacy” optical fiber nodes (204), and the digital optical datareconstituted (e.g. by optical-digital to analog-RF units, or by feedingthe digital QAM symbols into local QAM modulators). Both operations canbe done with minimal onboard intelligence at the optical fiber node,hence the “dumb” label. This “dumb” optical fiber

In FIG. 5, neighborhoods 1 and 2 are served by the invention's improved“smart” D-CMRTS/DOFN fiber nodes (300). By contrast, neighborhood 3 isonly served by a “dumb” legacy fiber node (204). This legacy fiber nodemay operate by simply converting analog optical fiber waveforms intotheir corresponding RF waveforms.

FIG. 6 shows one embodiment of the invention operating to send dataupstream. As previously discussed, at the CATV cable, considerably moreupstream data can be sent due to the previously discussed (but optional)methods of allocating more CATV bandwidth for upstream data (e.g. usingspectrum reallocation). Because spectrum reallocation is easier to draw,this larger amount of upstream data being transmitted along the CATVcable is symbolized here by the two dark dotted or dashed parabolaslabeled “upstream data” for neighborhoods 1 and 2, showing the higheramounts of upstream spectrum. By contrast, the smaller amount ofupstream data that can be transmitted using prior art methods issymbolized by the one dark parabola labeled “upstream data” forneighborhood 3. Here for example, perhaps neighborhood 3 is using thestandard US CATV upstream partition that allocates 5-42 MHz for upstreamdata, while neighborhoods 1 and 2 are using an alternate scheme such asallocating 5-85 MHz for CATV upstream data. Here for example, RF handler(606), which can have the functions of combining, splitting, orduplexing the various RF signals can be switched into an alternate modethat deviates from the present 5-42 MHz upstream and 54-870 MHzdownstream standards, and instead allocates the 5-85 MHz region forupstream, and for example the 92-870 MHz region for downstream.

As previously discussed, if the higher amount of upstream data wassimply transmitted back along the optical fiber system using the sameinefficient (for optical fiber) CATV signal modulation scheme (againusually QAM modulation), then the optical fiber itself would rapidlybecome a rate-limiting bottleneck. To avoid this problem, according tothe invention, the D-CMRTS/DOFN nodes may extract this upstream data,and repackage it into more efficiently (for optical fiber) modulatedGigE formats. Additionally or alternatively, according to the invention,digital switches (220D) or smart fiber combiners (220) may themselvestake the upstream data sent by the optical fibers (222) connectingvarious neighborhoods, and extract the upstream data and repackage theupstream data in a more efficiently modulated (for optical fiber) GigEformat.

Although much of the upstream content consists of relatively standardQAM waveforms, at least some legacy CATV systems can also provide avariety of unusual upstream RF waveforms, such as various QPSK channelsfrom various older set top boxes, OFDM waveforms, such as used forDOCSIS 3.1, and the like. However it is burdensome to try to parse eachand every possible upstream waveform for content. To avoid this burden,here again more general methods that simply digitize whatever waveformis seen can be useful.

Thus to be able to digitize, and optically transport upstream, apossibly wide variety of possible RF CATV waveforms, while at the sametime trying to conserve optical fiber bandwidth where feasible, in someembodiments, the digital optical fiber node (D-CMRTS unit) willadditionally have at least one of:

1: An RF digital converter device configured to accept upstream RFwaveforms transmitted over the CATV cable, and digitize these upstreamRF waveforms using, for example, a high speed analog to digitalconverter, and produce digitally encoded upstream RF channel data.

2: Since many upstream RF signals will be QAM waveforms, for opticalfiber bandwidth efficiency purpose, it is often desirable to also havean RF demodulator device configured to accept upstream RF QAM channelstransmitted over the CATV cable, and demodulate the RF QAM channels andproduce the upstream digital QAM symbols that originally were used toconstruct the various upstream QAM waveforms. The same can also be donefor OFDM waveforms as desired.

3: Additionally, for high performance, it is also often desirable tohave a QAM to IP conversion device configured to accept upstream digitalIP data packets transmitted by the upstream QAM RF channels over theCATV cable, and extract the upstream digital IP data packets, thusproducing upstream digital IP packets. The same can also be done forOFDM waveforms as desired.

Once this digital data has been produced, the digital optical fiber nodeor D-CMRTS/DOFN unit will also often have a digital data to opticalconverter device configured to combine any of these digitally encodedupstream RF channel data, upstream digital QAM symbols, and upstreamdigital IP packets and transmit this data, symbols, and packetsdigitally upstream over the optical fiber.

More specifically, note that the D-CMRTS/OFDM units themselves may, insome embodiments, use relatively simple digitization methods, such asRF-analog to optical-digital converters, or QAM demodulators, to extractupstream CATV RF signals, digitize them, and transmit them in a fiberdigital format such as GigE back to the head end. Here again, by simplygiving the data packets an appropriate label or header, it is relativelysimple to aggregate data from many D-CMRTS units, and send them all backupstream on the same optical fiber channel (as desired), again bothincreasing upstream data handing capability and also saving costs overalternative methods.

Thus in FIG. 6, the large amount of upstream data from neighborhood 1(400, dark dotted parabolas) and the large amount of upstream data fromneighborhood 2 (402, dark dashed parabolas), could in alternativeschemes have originally been sent upstream along optical fiber (222) byD-CMRTS Fiber Node 1 and D-CMRTS Fiber Node 2 (300) at various differentoptical fiber wavelengths to avoid interference.

However, since, according to the invention the D-CMRTS/DOFN units mayhave either repackaged and remodulated this upstream data into a moreefficient more optical fiber transmission GigE format, this data fromdifferent neighborhoods may instead be sent back using the same opticalfiber wavelength (if this option is desired, which it often may bebecause it is cheaper).

Note that although this disclosure has focused on the all digitaloptical fiber transmission aspects of the invention, this focus shouldnot be intended to exclude the fact that analog optical fibertransmissions may also co-exist along optical fiber (222).

Consider the case for neighborhood 3. In some schemes the D-CMTRS unitsor a prior art dumb fiber node (204) may simply and relativelypassively, have transuded the upstream CATV RF waveforms from RF tooptical signals such as infrared optical signals, and then retransmittedthe upstream data otherwise modulated “as is”.

Although this option is not excluded, in a preferred embodiment, thedumb optical fiber node (204) may either be replaced by a dumb digitalconverter optical fiber node that does little more than digitize theupstream CATV RF signal (e.g. using a module such as 601 or 605), andtransmit this digital data upstream on optical fiber (222) according tostandard optical fiber digital formats. As yet another embodiment, theprior art dumb optical fiber node (204) may be retained, but a digitalnode converter unit (401) may be put in place to convert optical fibersignals back and forth between a digital optical format and a legacyanalog format for the legacy dumb optical fiber node (204). Here, thisnode converter unit (401) may, in some embodiments, essentially do thesame type of data repackaging and remodulation functions of previousswitch (220) previously discussed in parent provisional applications61/385,125 and 61/511,395, the contents of which are incorporated hereinby reference. Alternatively the legacy optical fiber node (204) canremain connected to the head end by another legacy optical fiber (403)path, and the head end (202), which retains its legacy capabilities,will be able to adequately serve remaining legacy optical fiber nodes(204) during the upgrade process.

In the present disclosure, switch (220) is instead operating as a multiport digital data switch (220D), which may operate at either onewavelength or a plurality of wavelengths as desired, and the dataextraction, digitization or reconstitution functions, and analog formatto digital data packet repacking functions may instead be moved to otherdevices such as converters (399) and (401).

For example, in this scheme, the upstream data from neighborhood 1 (darkdotted parabolas) and the upstream data from neighborhood 2 (dark dashedparabolas) has been digitized and repackaged by the D-CMRTS/DOFN units(200) into various digital data packets.

Without such digital conversion, the two upstream data sources may havebeen originally sent by the various D-CMRTS units on different opticalwavelengths. But because the data has now been repackaged at the D-CMRTSunits, now the data from both neighborhoods can be carried upstream onoptical fiber digital data streams (308) and (312) at the samewavelength along optical fiber (301).

FIG. 7 shows a more detailed view of how the D-CMRTS fiber nodes (300),converters (399) and improved digital cable modem termination systems(D-CMTS) (500) at the cable head with improved D-CMTS line cards, mayoperate.

For simplicity, again primarily the downstream portion of the system isshown. Generally the D-CMRTS/DOFN units will have an onboard digitaldata switch (560) (operating either with optical fiber digital datapackets, the electrical version of these optical fiber digital datapackets) used to direct various optical fiber data packets to and fromtheir correct destination devices (e.g. 600, 601, 603, 604, 605, 607)inside the D-CMRTS/DOFN.

Although a capability of operating at multiple optical wavelengths isnot required, in an alternative embodiment where operating with aplurality of optical fiber wavelengths is desired, then the switch (560)may optionally also include optical fiber wavelength splitters, such asone or more Brag filters or other device, to separate out the variouswavelengths. These optical fiber wavelength splitters may optionally bea “smart” or tunable filter that may select different wavelengths undermicroprocessor and software control. The different wavelengths selectedby this splitter may then be sent to various subsystems, such as CMRTSunits (604), which can extract the digital data, repackage it, andgenerate CATV QAM signals and/or other RF signals for the CATV cable.

For backward compatibility, the D-CMRTS/DOFN fiber nodes (300), (304)may also have one or more simple optical-digital to analog RF (O-D/A-RF)(600) converters to convert any digitized legacy downstream opticalfiber data, which may contain analog to digital sampled versions ofvarious CATV NTSC, FM, QPSK, or even QAM waveforms back from digitaldata packets to their respective analog RF waveforms again. Depending onthe embodiment, (O-D/A-RF) converters may work directly on downstreamoptical data, or alternatively work on electrical equivalents of thedownstream optical data signals.

The D-CMRTS/DOFN fiber nodes may additionally contain the reverseupstream versions of these units (601). These upstream units will takeselected upstream RF signals from the CATV cable, such as set top boxQPSK channels or even DOCSIS upstream channels as needed, do an analogto digital conversion, fit into data packets, and optionally eithertransduce into upstream optical data packets, or allow a later stagedevice such as switch (560) to transduce into upstream optical datapackets to send back to the head end.

Also for backward compatibility, the D-CMRTS/DOFN fiber nodes (300),(304) may also have one or more QAM remodulator devices (603) to takedemodulated QAM symbols from the downstream optical data packets, andconvert these back into RF QAM waveforms carrying the same data payload,and then send downstream on the CATV system via RFcombiner/splitter/duplex (606). Again depending on the embodiment, theseQAM remodulator devices may work directly on optical data, oralternatively work on electrical equivalents of the optical datasignals.

These QAM remodulator devices may additionally contain the reverseupstream RF QAM demodulator versions of these units (605). Theseupstream QAM demodulator units may take selected upstream QAM RF signalsfrom the CATV cable, such as various legacy DOCSIS upstream QAM channelsas needed, demodulate the RF QAM waveforms to extract the underlying QAMsymbols that generated the waveforms, fit these demodulated upstream QAMsymbols into data packets, and optionally either transduce these QAMsymbols into upstream QAM symbol optical data packets, or allow a laterstage device such as switch (560) to transduce into upstream QAM symboloptical data packets to send back to the head end.

The D-CMRTS units may additionally contain one or more optical datapackets (e.g. optical IP data packets) to RF QAM waveform converters(607). These IP to QAM converters are useful for, example, convertinglegacy broadcast QAM channels from the head end that have beendemodulated at the head end and packaged into optical data packets formore compact (e.g. lower bandwidth needed) transport over the opticalfiber than would be possible than if the entire legacy head end analogQAM channel waveforms had instead been transposed to equivalent opticalQAM waveforms. In some embodiments (not shown), the D-CMRTS units mayalso contain the reverse version of these units that takes upstream QAMRF data, demodulates it, repackages the upstream QAM symbols into IPdata packets for optical upstream transmission.

The D-CMRTS/DOFN fiber node (304) may also contain one or more CMRTSunits (604) that may select at least some of the GigE formatted data(310), (310), (307) from the optical fiber (222) QAM modulate this data,and send it to the CATV cable. (226) according to the scheme previouslydiscussed in FIG. 4D. The CMRTS (604) portion of the D-CMRTS unit (304)may in some embodiments generally function as previously discussed incopending application Ser. No. 12/692,582, the contents of which areincorporated herein by reference.

Although again, a key advantage of the system is that at least in theinitial upgrade stages, it can be made almost totally transparent (i.e.capable of running with) legacy HFC software, it should be appreciatedthat to provide additional functionality, further software upgrades maybe desirable. Here, such an upgraded mix and match system will impose aconsiderable configuration and management problem on the D-CMTS units atthe cable head (202). As previously discussed in parent application Ser.No. 12/692,582 and also in the present specification, this complexitymay be handled by a computerized network management system and softwaretermed the “virtual shelf”.

In one embodiment of the improved “virtual shelf” system, the D-CMTSshelf and improved D-CMTS line cards may optionally be configured withboth packet processors (610), and MAC (612) and PHY (614) devices orfunctionality to transmit standard CATV analog, QAM, NTSC, QPSK, andDOCSIS analog signals, where the signals may be digitized by converter(399) and transported over the optical fiber as a series of legacyoptical IP data packets (307).

The same CMTS shelf and line cards may also be configured with packetprocessors (616), MAC (618) and PHY (620) functionality to some or allof this data as GigE formatted data as various digital optical IP datastreams (e.g. 308, 310, 312) on one or optical fiber wavelengths.

As a result, the MAC (618) and PHY (620) for (308, 310, 312) can bedifferent from the MAC (612) and PHY (614) used for the optical fiber IPdata packets for the legacy signals (307).

The exact mix of signals transmitted and received by the improved linecard will vary depending upon what sort of fiber nodes are connecteddownstream (southern end) to the line card.

For example, if all of the fiber nodes were “dumb” prior art fiber nodes(204), then the D-CMTS line card may only transmit legacy digitizedoptical IP data packets (307), and after passing through converter (399)the functionality of that particular D-CMTS line card could be backwardcompatible with prior art CATV DOCSIS equipment and fiber nodes.

That is, the optical fiber legacy IP data stream (307) could transmitthe full set of DOCSIS channels, simply by brute force analog todigital, digital optical transmission, and digital to analog conversion;and/or brute force QAM demodulation into QAM symbols, digital opticaltransmission, and QAM symbol remodulation back into QAM waveformmethods.

By contrast, if all of the fiber nodes were “smart” improvedD-CMRTS/DOFN fiber nodes (300), then the improved head end D-CMTS andCMRTS line card might elect to maximize all or nearly all data to thevarious households by skipping legacy mode, just sending all data viathe non legacy optical IP data packets (308, 310, 312) one or morewavelengths in an optical digital transport protocol such as GigEformat, and leave it to the D-CMRTS units (300), (304) to then handlethe reformatting and conversion to CATV RF modulation schemes such asQAM modulation.

This scheme would thus allow the highest amount of customized data to besent to the houses on that particular stretch of cable.

In a mixed mode HFC system using a mix of “dumb” fiber nodes (204) and“smart” CMRTS fiber nodes (300) (as previously shown in FIG. 5), theimproved D-CMTS and D-CMTS line cards could ideally elect to operate inboth legacy and GigE modes, thus transmitting and receiving standardvideo channels (114) and DOCSIS (116) information to and fromneighborhood 3 (served by the “dumb” fiber node), using the digitalconverter (399), optical node converter (401), and the legacy opticalfiber digital IP packet data stream (307) to continue giving adequateservice to neighborhood 3.

As previously discussed, in order to manage this complexity, thefunctionality of the improved head end D-CMTS and D-CMTS line cards, aswell as usually the functionality of the D-CMRTS fiber nodes (300), maybe extended by use of additional “virtual shelf” network managementcomputers, controllers, and software.

In one embodiment, a unified network management system (exemplified by,for example, the ConfD management system provided by Tail-fincorporated) is added to the improved D-CMTS and line card to unify thenetwork and D-CMTS hardware and virtualization layer, provide operatingsystem services, manage middleware, and configure the system to use theproper networking protocols. In this embodiment, all or at least muchnetwork configuration data is stored on a database in the D-CMTSmanager, and the configuration of the network is controlled by a processin which the management software (ConfD) communicates over IPC (sockets)with apps that control the function of various packet processors, MAC,and PHY devices on the improved D-CMTS and D-CMRTS/DOFN units.

Here the a computer or processor and associated software memory (622)are shown directly controlling the operation of an improved D-CMTS unitby way of various other controllers (624), (626) located in the improvedD-CMTS backbone and line cards (500). The communications between this“virtual shelf manager” (622) and the local controller processors (624),(626) are shown as dashed lines (628). The virtual shelf manager mayalso control the operation of a level 2/3 switch (629) and/or otherdevices that connect the improved D-CMTS unit to the media content(210), IP backbone “cloud” (212), and other services provided by thecable head (202).

The virtual shelf manager may often also manage the configuration of thevarious “smart” D-CMRTS/DOFN fiber nodes (300), often by communicatingwith controllers and applications software embedded with theD-CMRTS/DOFN fiber nodes (not shown). Given the typically long distancesbetween the D-CMRTS/DOFN fiber nodes (300) and the virtual shelf manager(622) and improved D-CMRT (500) (which will often be located at thecable head, miles or more away from the various nodes (300)), theD-CMRTS/DOFN fiber node (300) to virtual shelf manager (622)communication will often be done by various signals and signal protocolscommunicated by the optical fiber or fibers. In one preferredembodiment, socket based inter-process communication (IPC) protocols areused.

This enables the configuration of the D-CMTS shelf, and indeed theoverall network, to be rapidly reconfigured to meet the ever changingnetwork model generated by the invention. Often it will be convenient tostore this network configuration, as well as the properties of thevarious network devices, in a configuration database (630) andconfiguration database memory device (not shown).

FIG. 8 shows more details of the Cable Modem Remote Termination SystemCMRTS (604) portion of the D-CMRTS/DOFN fiber node. At a higher or atleast alternate level of abstraction, at least the CMRTS portion of theD-CMRTS/DOFN fiber node, and often the entire circuitry in the DOFNdevice may typically comprise at least a first set of QAM-RF packetprocessors (700) with MAC and PHY units that select the desired opticalIP downstream data from the GigE formatted data, and convert thedownstream optical IP packet data to a plurality of radiofrequency (RF)QAM waveforms (channels) and output this data downstream (702) to thelocal CATV cable.

This CMRTS unit (604) may also optionally comprise a second set ofRF-upstream packet processors (704) that will read the upstream RFsignals (data) sent by cable modems connected to the local CATV cable(706). Note that these packet processors (704) may contain MAC and PHYunits that are capable of recognizing the upstream data. Thus if theupstream data is sent using an unusually wide upstream bandwidthaccording to scheme (390), the MAC and PHY units will recognize it. Theunits will then convert this upstream data to appropriate optical IPEthernet data packets, or other digital optical data communicationsprotocols suitable for communicating this cable modem data back upstreamto the improved D-CMTS (500) at the cable head.

The operation the DOFN, as well as both packet processors (700), (704)as well as other devices such as O-D/A-RF or RF-A/D-O converters (600),(601), QAM remodulators and demodulators (603), (605), CMRTS unit (604)and the like may be remotely controlled by the virtual shelf manager(622) by way of suitable controllers (often microprocessors), and localapplications software (Apps) that intercept data from the optical fiber(222) and receive and send commands, often by way of a specializedcommunications protocol such as the previously discussed socketsprotocol.

At a deeper level that exposes more details of the PHY units in both theQAM-RF packet processor (700) and the optional RF-upstream packetprocessor (704), The DOFN's CMRTS unit (604) will normally comprise MACand PHY units, and a data switch (710), at least one controller (often amicroprocessor and associated software, not shown), various QAMmodulators (712) to take the GigE data and convert, QAM modulate, andfrequency shift the data as needed to fit the limited CATV RF bandwidth.To do this, DOFN's CMRTS unit may employ a controllable clock generator(714) to control the frequency and timing of the QAM channels, as wellas variable gain amplifier (VGA) units (716), (718) to help the PHYportions of the units manage the analog processes in converting signalsback and forth between the CMRTS/DOFN unit (300) and the cable RFsignals.

Various network timing protocols may be used to synchronize the varioushead end units, DOFN and other HFC network components. In someembodiments, it may be useful to employ the IEEE-1588™ standard tosynchronize the various network real time clocks, however otherprotocols, such as the Network Time Protocol, RFC 1305 (NTP), Satellitebased Global Positioning System (GPS), TTP, and SERCOS (IEC 61491) mayalso be used.

As before, the MAC and PHY units and the data switch (710) switches, andthe switches that control the QAM modulators (712) and analog to digital(A/D) units (720) may be remotely controlled by the virtual shelfmanager (622) by local (embedded) controllers (often microprocessors)and associated applications software by commands to and from the VirtualShelf software. As before, often these commands may be sent over thesame optical fiber pathways normally used to transmit other data, andagain may use socket based inter-process communication (IPC) protocols.

As before, for backward compatibility, the return process for processingupstream data can optionally implement the RF-A/D-O converters (601)and/or QAM demodulators (605) digitize and send the upstream signalsback with essentially no modification other than digitization, datapacket conversion, and optical conversion process.

Generally, the upstream data will be detected by whatever equipment isbest suited to interpret the invention's various upstream datamodulation methods—e.g. suitable equipment to intercept and decode thewider bandwidth upstream data and the like.

In this scheme, for simplicity, it is assumed that these methods will beimplemented by high speed DSP or software controlled receiver that canamplify the various signals, digitize them, and then decode according tothe appropriate algorithms, but of course other methods may also beused. Other hardware, such as ASICs, FPGA, DSP, and the like may also beused, as per U.S. patent application Ser. No. 13/555,170, the contentsof which are incorporated herein by reference.

In one embodiment, variable gain amplifier (VGA) units (718) willconvert the incoming upstream RF signal from the local neighborhood CATVcable into a signal which is then digitized by the A/D converter andclock generator, analyzed and repackaged by the MAC and PHY units (710)into a GigE or other optical fiber optimized signal, and then sentupstream along the optical fiber through various optical fibersplitter/combiner units (710). This process may be controlled bycommands from the Virtual Shelf software.

FIG. 9 shows more details of how the virtual shelf manager (622) and theconfiguration database (630) (previously shown in FIG. 7) may controlthe functionality of most or all of the plurality of D-CMRTS/DOFN fibernodes (300), improved D-CMTS (500) D-CMTS line cards (502), andoptionally other active nodes and switches in the HFC network system.

In this example, the virtual shelf manager software (622) is shownrunning as a module of a broader D-CMTS manager software package (800);however it also may be run as a standalone package. The D-CMTS managersoftware (800), which will often be run on one or more computerprocessors which may be located at the cable head or other convenientlocation, will often be based on network configuration managementsoftware (802). Such network configuration software (802) (also calledthe Operational Support Systems (OSS) software) may be, for example,software based upon the ConfD network management software produced byTail-f Systems Corporation, Stockholm Sweden (International location)and Round Hill Va. (US location).

In this embodiment, use of software such as ConfD is useful because thistype of network management software also provides a number of convenientand commonly used interfaces to allow users to interact with the networkand control then network configuration. These interfaces may includeNETCONF management agents, SNMP agents, Command Line Interfaces (CLI),Internet (Web) interfaces, and other agents/interfaces as desired.

The virtual CMTS shelf software that may be used to control the statusof the various D-CMTS line cards (500) and D-CMRTS/DOFN fiber nodes(300) will often interact with a network configuration database (630)run under the control of this network configuration software (802). Thevirtual D-CMTS shelf software will in turn send commands out to most orall of the various remote D-CMRTS/DOFN fiber nodes, as well as controlthe operation of the D-CMTS (500) at the cable head and other devices asdesired. As previously discussed, one preferred way for this control tobe achieved is by way of socket based inter-process communication (IPC)protocols and packets (804), which may be sent over the same opticalfiber lines used to send the other data. In this situation, for example,controllers running various types of application software (Apps) in theplurality of remote packet processors (700), (704) in the remote D-CMRTSfiber nodes (300) can listen for appropriate commands from the virtualshelf manager (622), and adjust the operation of the D-CMRTS packet(700), (704) processors accordingly. These D-CMRTS fiber nodes can alsotransmit their status back to the virtual shelf manager using the sameprotocols.

The device configuration database (630) of the virtual shelf managersystem will often have multiple data fields, including fields thatcontain the identification code and/or addresses of the various D-CMRTSunits in the network (D-CMRTS identifier fields). The database will alsousually have information on the status of the various cable modemsconnected to the various D-CMRTS units, including the cable modemidentification data (cable modem identification data fields) and theprivileges of the various users that are associated these various cablemodems. For example, one user may have privileges to access a broadarray of services high bandwidth upload and download data, while anotheruser may have limited access to a different set of services and morelimited upload and download data privileges. Other functions that may beimplemented include event logging, Authentication, Authorization andAccounting (AAA) support, an extended version of a DOCSIS ManagementInformation BASE (MIBs) functions, etc.

Other fields that normally will be in the database will includeinformation as to user identification fields (user privilege fields),available extended DOCSIS channels, available IP addresses, instructionsfor how to remotely configure the various D-CMRTS software controllableswitches, and instructions for how to remotely configure the variousD-CMRTS/DOFN software controllable RF packet processors.

The virtual shelf manager and configuration database, as well as othercomponents of the system, will usually be run on a computer system withat least one microprocessor, as well as standard hardware and software,such as MAC and PHY units, that will enable the virtual shelf manager tosend and receive data packets (often through the IPC protocol) to thevarious remote D-CMRTS/DOFN units on the network.

The OSS software (802) can inform the virtual shelf manager softwareabout the privileges, certificates, and encryption keys assigned to thevarious users. The OSS can also set policies or allocation limitsregarding the frequency and bandwidth that will be assigned to thevarious channels. The OSS can also respond to queries from the virtualshelf manager when new modems are detected. The OSS can further takestatistical data collected by the virtual shelf manager, such as packetstransmitted and received, volume of data, and use this information forbilling and network management purposes.

Further information on OSS functions, and more examples of functionsthat may be implemented in the OSS software for the invention, may befound in Misra, “OSS for Telecom Networks: An Introduction to NetworkManagement”, Springer (2004).

For example how this system would operate, consider the case where a newcable modem is first connected to the system. The cable modem may sendan upstream signal (226) to the D-CMRTS (604). The RF-up packetprocessor (704) in the DCMRTS (604) will in turn collect the informationrelating to the cable modem identification number, and other relevantparameters, repackage the data in a digital format, and send it backupstream to the virtual shelf manager system on the fiber GigE link(302). The virtual shelf manager system (622) will look up the cablemodem identification data in the device configuration database (630),and determine the privileges of the user associated with the cable modemidentification data, and depending upon the value of the user privilegefield, available extended DOCSIS channels, and available IP addresses,send data packets to the D-CMRTS (700) unit, often by way of the IPCprotocol (804) that controls that particular cable modem. The virtualshelf manager may also control the function of any household gatewaydevices.

These data packets will interact with applications (e.g. App 1, App n)and configure the software controllable switch(s) on the D-CMRTS unit(700), to configure the software controllable switches on the QAM-RFpacket processor (700) and the cable modem available IP addresses orTDD-FDD gateway addresses so as transmit downstream data to the cablemodem on a first available DOCSIS channel. The data packets will alsoconfigure the software controllable RF packet processor (704) to receiveupstream data from the cable modem on a second available DOCSIS upstreamchannel and IP address and retransmit the upstream data as a thirdupstream digital optical fiber signal (302).

Often the virtual shelf manager (622) will handle IP addresses for thecable modems and optional gateway devices through the proxy Dynamic HostConfiguration Protocol (DHCP) service, or other method.

Alternative types of residential gateways capable of allowing householdCATV equipment that is designed for the standard DOCSIS CATV protocolsthat call for the 5-42 MHz range of upstream frequencies to work withCATV cables an extended range of upstream frequencies are also possible.This gateway equipment will be designed to “fool” the household CATVequipment into thinking that it is connected to a standard CATV cablethat is capable of carrying standard 5-42 MHz upstream data, but thatthis standard CATV cable is relatively uncongested—that is that acomparatively large portion of the 5-42 MHz spectrum is free for use. Infact, the gateway equipment may then either shift the frequency of thehousehold 5-42 MHz upstream data (e.g. QAM channels) to an alternatefrequency (e.g. convert a 20 MHz upstream QAM channel to, for example, a100 MHz QAM channel) for transmission over the CATV cable, oralternatively convert the upstream QAM channel(s) into spread spectrumsignals. In either event, the converted upstream signals will then besent upstream on the CATV cable to the D-CMRTS optical fiber node, orother fiber node as appropriate. This data may then be converted tooptical fiber data and sent on to the cable head as appropriate.

Adaptive cancellation methods, useful for such adjustableupstream/downstream frequency ranges were taught in copendingapplication Ser. No. 13/400,415 “METHODS OF ADAPTIVE CANCELLING ANDSECONDARY COMMUNICATIONS CHANNELS FOR EXTENDED CAPABILITY HFC CABLESYSTEMS”, the contents of which are incorporated herein by reference.

FIG. 10 shows an alternate type of residential gateway (1100) that canconvert between a CATV cable system with an extended frequency allocatedfor upstream data (e.g. 5-547 MHz or alternative upstream range offrequencies), and residential equipment designed for the standard 5-42MHz range of upstream frequencies.

Here CATV cable 226 is carrying extended range frequency upstream data(390), which may have far more upstream MHz bandwidth than the standardlimited CATV 5-42 MHz upstream bandwidth. However the problem is thatwithin the household, the CATV equipment—e.g. set top boxes, cablemodems, may be legacy CATV equipment that only is capable of sendingupstream data on the standard 5-42 MHz bandwidth. In this example, thegateway (1100) serving the house may be an extended FDD upstream gatewaythat contains the equipment necessary to frequency shift the householdCATV equipment upstream signals to alternate frequencies forretransmission on the CATV cable (226). Thus, for example, the upstreamdata capability of a neighborhood could be extended about 10× byreallocating and transmitting the normal 5-42 MHz upstream data in abroader 5-547 MHz range, and tricking every household into thinking thatit had free access to a 5-42 MHz upstream range of frequencies that wasonly 1/10 as congested as it was before.

As previously discussed, alternate types of gateways are also possible.Such alternative methods were discussed in application Ser. No.13/555,170, which was a CIP of application Ser. No. 13/035,993 “METHODOF CATV CABLE SAME-FREQUENCY TIME DIVISION DUPLEX DATA TRANSMISSION”,now U.S. Pat. No. 8,365,237, the contents of these applications areincorporated herein by reference.

Other alternative embodiments of the invention are also possible. Inthese alternative embodiments, the CMRTS or D-CMRTS/DOFN units can havemultiple outputs, such as multiple CATV cable outputs, or even a mix ofCATV or Coax cable outputs and, other output types such as data outputs(e.g. GigE or other data output), telephony outputs, and the like.

Other applications: The present invention may also be used foralternative HFC configurations, such as copending application Ser. No.13/346,709 “HFC CABLE SYSTEM WITH WIDEBAND COMMUNICATIONS PATHWAY ANDCOAX DOMAIN NODES”, and Ser. No. 12/907,970 “HFC CABLE SYSTEM WITHSHADOW FIBER AND COAX FIBER TERMINALS”, the contents of which areincorporated herein by reference.

1. A method of digitally transmitting downstream data over at least theoptical fiber portion of a Hybrid Fiber Cable (HFC) network, said HFCnetwork comprising at least a head end and at least one digital opticalfiber node (DOFN) that is connected to at least one set of neighborhoodCATV cables, and wherein said data comprises downstream QAM channels,said method comprising: transmitting at least one downstream QAM channelover the optical fiber as a plurality of QAM constellation symbols byencapsulating said QAM constellation symbols into a plurality ofEthernet frames or other digital transmission format frames, anddigitally transmitting said plurality of Ethernet frames or otherdigital transmission format frames over said optical fiber; using saidDOFN to receive said plurality of Ethernet frames or other digitaltransmission format claims, extract said downstream QAM constellationsymbols, and use said downstream video QAM constellation symbols tomodulate at least one DOFN QAM modulator, thus producing downstream QAMRF signals, and transmitting said DOFN generated downstream QAMmodulated RF signals further downstream over said at least one set ofneighborhood CATV cables.
 2. The method of claim 1, wherein said QAMchannels comprise either video QAM channels, video Edge-QAM channels, orIP-QAM channels.
 3. The method of claim 1, wherein said downstream datafurther comprises National Television System Committee (NTSC) orOrthogonal Frequency Division Multiplexing (OFDM) RF channels, andfurther digitally transmitting said data over said optical fiber by:digitally sampling said NTSC or OFDM RF channels at said head end,producing a plurality of digitized waveform data, encapsulating saiddigitized waveform data into a plurality of digitized waveform datacontaining Ethernet frames or other digital transmission frames, anddigitally transmitting said plurality of digitized waveform datacontaining Ethernet frames or other digital transmission framesdownstream over said optical fiber; using said DOFN to receive saidplurality of digitized waveform data containing Ethernet frames or otherdigital transmission frames, extract said plurality of digitizedwaveform data, and use said plurality of digitized waveform data todrive at least one digital to analog converter, thus producingdownstream NTSC or OFDM RF channels; and further transmitting said DOFNgenerated NTSC or OFDM RF signals further downstream over said at leastone set of neighborhood CATV cables.
 4. The method of claim 1, whereinsaid downstream data further comprises Orthogonal Frequency DivisionMultiplexing (OFDM) RF channels and further digitally transmitting saiddata over said optical fiber by: demodulating said OFDM RF channels atsaid head end, producing a plurality of OFDM symbols, encapsulating saidplurality of OFDM symbols into a plurality of OFDM symbol carryingEthernet frames or other digital transmission frames, and digitallytransmitting said OFDM symbol carrying Ethernet frames or other digitaltransmission frames downstream over said optical fiber; using said DOFNto receive said plurality of OFDM symbol carrying Ethernet frames orother digital transmission frames, extract said plurality of OFDMsymbols, and using said plurality of OFDM symbols to drive at least oneOFDM RF modulator, thus producing downstream OFDM RF channels; andfurther transmitting said DOFN produced OFDM RF signals furtherdownstream over said at least one set of neighborhood CATV cables. 5.The method of claim 1, further used to digitally transmit upstream RFQAM channel data originating from at least one cable modem or otherneighborhood CATV cable connected devices, over said optical fiber, by:at said DOFN, receiving said upstream RF QAM channel data, anddemodulating said at least one upstream RF QAM channel into a pluralityof upstream QAM constellation symbols; encapsulating said plurality ofupstream QAM constellation symbols into a plurality of Ethernet framesor other digital transmission format frames; and using said opticalfiber to digitally transmit said plurality of Ethernet frames or otherdigital transmission format frames upstream to said head end.
 6. Themethod of claim 1, further used to digitally transmit upstream RF OFDMchannel data, originating from at least one cable modem or otherneighborhood CATV cable connected devices, over said optical fiber, by:at said DOFN, receiving said upstream RF OFDM channel data, anddemodulating said at least one upstream RF OFDM channel into a pluralityof upstream OFDM symbols; encapsulating said plurality of upstream OFDMsymbols into a plurality of Ethernet frames or other digitaltransmission format frames; and using said optical fiber to digitallytransmit said plurality of Ethernet frames or other digital transmissionformat frames to upstream said head end.
 7. The method of claim 1,further used to digitally transmit upstream RF channel data, and furtherdigitally transmitting said data over said optical fiber by: at saidDOFN, receiving said upstream RF channel data, digitally sampling saidRF channel data producing a plurality of digitized waveform data;encapsulating said digitized waveform data into a plurality of Ethernetframes or other digital transmission frames; and using said opticalfiber to digitally transmit said plurality of Ethernet frames or otherdigital transmission frames upstream to said head end.
 8. The method ofclaim 1, used to upgrade a legacy Hybrid Fiber Cable (legacy HFC) systempreviously configured to transmit data downstream over said opticalfiber using analog optical QAM waveforms, said legacy HFC systemcomprising: a head end configured to produce downstream RF QAMwaveforms; a legacy fiber optic transmitter system configured totransduce said RF QAM waveforms into downstream analog optical QAMwaveforms; wherein said optical fiber is configured to transmit saidanalog optical QAM waveforms downstream to at least one legacy opticalfiber node; wherein said at least one legacy optical fiber node isconfigured to receive said downstream analog optical QAM waveforms,transduce said analog optical QAM waveforms into RF QAM waveforms, andtransmit said RF QAM waveforms downstream over said at least one set ofneighborhood CATV cables; said method further comprising: replacing saidat least one legacy optical fiber node with at least one DOFN; replacingsaid legacy fiber optic transmitter system with a demodulator anddigital fiber optic transmitter system configured to demodulate saiddownstream RF QAM waveforms into a plurality of QAM constellationsymbols; said digital fiber optic transmitter system further configuredto transmit at least one downstream RF QAM channel over said opticalfiber as a plurality of QAM constellation symbols encapsulated into aplurality of Ethernet frames or other digital transmission format framesusing a digital optical transmission method.
 9. The method of claim 8,wherein said downstream RF QAM channels comprise either video QAMchannels, video Edge-QAM channels, or IP-QAM channels.
 10. The method ofclaim 8, wherein said downstream data further comprises NationalTelevision System Committee (NTSC) or Orthogonal Frequency DivisionMultiplexing (OFDM) RF channels; wherein said digital fiber optictransmitter system is further configured to digitally sample said NTSCor OFDM RF channels at said head end, producing a plurality of digitizedwaveform data, encapsulate said digitized waveform data into a pluralityof digitized waveform data containing Ethernet frames or other digitaltransmission frames, and digitally transmit said plurality of digitizedwaveform data containing Ethernet frames or other digital transmissionframes downstream over said optical fiber using a digital optical formatto said DOFN; wherein said DOFN is further configured to receive saidplurality of digitized waveform data containing Ethernet frames or otherdigital transmission frames, extract said plurality of digitizedwaveform data, and use said plurality of digitized waveform data todrive at least one digital to analog converter, thus producingdownstream NTSC or OFDM RF channels for downstream injection into saidneighborhood CATV cable.
 11. The method of claim 8, wherein saiddownstream data further comprises Orthogonal Frequency DivisionMultiplexing (OFDM) RF channels; wherein said digital fiber optictransmitter system is further configured to demodulate said OFDM RFchannels at said head end, producing a plurality of OFDM symbols,encapsulate said plurality of OFDM symbols into a plurality of OFDMsymbol carrying Ethernet frames or other digital transmission frames,and digitally transmit said OFDM symbol carrying Ethernet frames orother digital transmission frames over said optical fiber using adigital optical format to said DOFN; wherein said DOFN is furtherconfigured to receive said plurality of OFDM symbol carrying Ethernetframes or other digital transmission frames, extract said plurality OFDMsymbols, and use said plurality of OFDM symbols to drive at least oneOFDM modulator, thus producing downstream OFDM RF channels fordownstream injection into said neighborhood CATV cable.
 12. The methodof claim 8 further used to upgrade said legacy HFC system to alsodigitally transmit, over said optical fiber, upstream RF QAM channeldata, said upstream RF QAM channel data originating from at least oneset of cable modem or other neighborhood CATV cable connected devices;wherein said DOFN is further configured to receive at least one upstreamRF QAM channel from said neighborhood CATV cable, demodulate said leastone upstream RF QAM channel into a plurality of upstream QAMconstellation symbols, encapsulate said plurality of upstream QAMconstellation symbols into a plurality of Ethernet frames or otherdigital transmission format frames, and use said optical fiber todigitally transmit said plurality of Ethernet frames or other digitaltransmission format frames upstream to said head end.
 13. The method ofclaim 8, further used to upgrade said legacy HFC system to alsodigitally transmit, over said optical fiber, upstream RF OFDM channeldata, said upstream RF OFDM channel data originating from at least oneset of cable modem or other neighborhood CATV cable connected devices:wherein said DOFN is further configured to receive at least one upstreamRF OFDM channel from said neighborhood CATV cable, demodulate said atleast one upstream RF OFDM channel into a plurality of upstream OFDMsymbols, encapsulate said plurality of upstream OFDM symbols into aplurality of Ethernet frames or other digital transmission formatframes; and use said optical fiber to digitally transmit said pluralityof Ethernet frames or other digital transmission format frames upstreamto said head end.
 14. The method of claim 2, further used to digitallytransmit upstream RF channel data, and further digitally transmittingsaid data over said optical fiber by: at said DOFN, receiving saidupstream RF channel data, digitally sampling said RF channel dataproducing a plurality of digitized waveform data; encapsulating saiddigitized waveform data into a plurality of Ethernet frames or otherdigital transmission frames; and using said optical fiber to digitallytransmit said plurality of Ethernet frames or other digital transmissionframes upstream to said head end.
 15. A method of upgrading a legacyHybrid Fiber Cable (legacy HFC) system previously configured to transmitdata downstream over an optical fiber using analog optical QAMwaveforms, to a digital HFC system configured to transmit datadownstream over said optical fiber using digital optical transmissionmethods; wherein said legacy HFC system comprises: a head end configuredto produce downstream RF QAM waveforms; a legacy fiber optic transmittersystem configured to transduce said RF QAM waveforms into downstreamanalog optical QAM waveforms; wherein said optical fiber is configuredto transmit said analog optical QAM waveforms downstream to at least onelegacy optical fiber node; wherein said at least one legacy opticalfiber node is configured to receive said downstream analog optical QAMwaveforms, transduce said analog optical QAM waveforms into RF QAMwaveforms, and transmit said RF QAM waveforms downstream over said atleast one set of neighborhood CATV cables; said method comprising:providing a demodulator to demodulate downstream RF QAM waveforms into aplurality of QAM constellation symbols: replacing said legacy fiberoptic transmitter system with a digital fiber optic transmitter systemconfigured to transmit at least one downstream QAM channel over saidoptical fiber as a plurality of QAM constellation symbols byencapsulating said QAM constellation symbols into a plurality ofEthernet frames or other digital transmission format frames, anddigitally transmitting said plurality of Ethernet frames or otherdigital transmission format frames over said optical fiber; andreplacing said at least one legacy fiber optic node with a digitaloptical fiber node (DOFN) configured to receive said plurality ofEthernet frames or other digital transmission format claims, extractsaid downstream QAM constellation symbols, and use said downstream videoQAM constellation symbols to modulate at least one DOFN QAM modulator,thus producing downstream QAM RF signals.
 16. The method of claim 15,wherein said QAM channels comprise either video QAM channels, videoEdge-QAM channels, or IP-QAM channels.
 17. The method of claim 15,wherein said downstream data further comprises National TelevisionSystem Committee (NTSC) or Orthogonal Frequency Division Multiplexing(OFDM) RF channels, and further digitally transmitting said data oversaid optical fiber by either: 1: digitally sampling said NTSC or OFDM RFchannels at said head end, producing a plurality of digitized waveformdata, encapsulating said digitized waveform data into a plurality ofdigitized waveform data containing Ethernet frames or other digitaltransmission frames, and digitally transmitting said plurality ofdigitized waveform data containing Ethernet frames or other digitaltransmission frames downstream over said optical fiber; using said DOFNto receive said plurality of digitized waveform data containing Ethernetframes or other digital transmission frames, extract said plurality ofdigitized waveform data, and use said plurality of digitized waveformdata to drive at least one digital to analog converter, thus producingdownstream NTSC or OFDM RF channels; and further transmitting said DOFNgenerated NTSC or OFDM RF signals further downstream over said at leastone set of neighborhood CATV cables; or 2: when said downstream datafurther comprises Orthogonal Frequency Division Multiplexing (OFDM) RFchannels and further digitally transmitting said data over said opticalfiber by: demodulating said OFDM RF channels at said head end, producinga plurality of OFDM symbols, encapsulating said plurality of OFDMsymbols into a plurality of OFDM symbol carrying Ethernet frames orother digital transmission frames, and digitally transmitting said OFDMsymbol carrying Ethernet frames or other digital transmission framesdownstream over said optical fiber; using said DOFN to receive saidplurality of OFDM symbol carrying Ethernet frames or other digitaltransmission frames, extract said plurality of OFDM symbols, and usingsaid plurality of OFDM symbols to drive at least one OFDM RF modulator,thus producing downstream OFDM RF channels; and further transmittingsaid DOFN produced OFDM RF signals further downstream over said at leastone set of neighborhood CATV cables.
 18. The method of claim 15, furtherused to digitally transmit upstream RF QAM channel data, RF OFDM channeldata, or any upstream RF channel data originating from at least onecable modem or other neighborhood CATV cable connected devices, oversaid optical fiber, by either: 1: at said DOFN, receiving said upstreamRF QAM channel data, and demodulating said at least one upstream RF QAMchannel into a plurality of upstream QAM constellation symbols;encapsulating said plurality of upstream QAM constellation symbols intoa plurality of Ethernet frames or other digital transmission formatframes; and using said optical fiber to digitally transmit saidplurality of Ethernet frames or other digital transmission format framesupstream to said head end; or 2: at said DOFN, receiving said upstreamRF OFDM channel data, and demodulating said at least one upstream RFOFDM channel into a plurality of upstream OFDM symbols; encapsulatingsaid plurality of upstream OFDM symbols into a plurality of Ethernetframes or other digital transmission format frames; and using saidoptical fiber to digitally transmit said plurality of Ethernet frames orother digital transmission format frames to upstream said head end; or3: at said DOFN, receiving said upstream RF channel data, digitallysampling said RF channel data producing a plurality of digitizedwaveform data; encapsulating said digitized waveform data into aplurality of Ethernet frames or other digital transmission frames; andusing said optical fiber to digitally transmit said plurality ofEthernet frames or other digital transmission frames upstream to saidhead end.
 19. The method of claim 18, further compressing any of thedigitally sampled or demodulated data prior to digital optical fibertransmission, and decompressing any of said compressed digitally sampledor demodulated data subsequent to digital optical fiber transmission.20. The method of claim 15, wherein after replacing said at least onelegacy fiber optic node with a digital optical fiber node (DOFN),further replacing said head end configured to produce downstream RF QAMwaveforms with an alternative head end configured to directly producevideo QAM constellation symbols without the need to employ a demodulatorto demodulate RF QAM waveforms into a plurality of QAM constellationsymbols.